LT1 cooling info

grumpyvette

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Staff member
READ THIS THREAD ALSO
viewtopic.php?f=57&t=832

http://shbox.com/1/component_location_views.html

http://garage.grumpysperformance.co...nvert-gen-i-sbc-to-reverse-flow-cooling.6099/

http://www.chevyhardcore.com/news/r...s-changing-your-small-block-worth-the-effort/

http://garage.grumpysperformance.co...-engine-parts-differences-useful-links.13141/
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95-97_hoses.jpg

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lt1asd


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Ok, maybe some of you will now understand what angles and spacing I am talking about when I say you can and can not do somethings. I didnt have a set of Vortec 350 heads laying around so I used a set of 305 heads which doesnt use the same intake design(actually they are still swirl port junkers) but does use the same bolt pattern.

Pic one, is a Lt1 head, notice that the bolt angle is not flush with the intake face.
lt1q1.jpg



Now here is the same head next to a standard SBC head, notice the bolt angle as compared to the SBC gen 1 head, also notice the spacing is different between the two heads. LT1 head is on the left, SBC GEN1 head is on the right. Also notice there is no water jacket on the intake face of the LT1
lt1q2.jpg



Here is a SBC GEN1 head next to the LT1 head..This is the deck surface, notice all the water jacket openings are different..SBC Gen1 head is on the left, LT1 on the right
lt1q3.jpg



Now there two are for the vortec head, notice that the bolts are even more of an angle than the LT1, when you bolt this intake on, the bolts are facing straight down, also notice there are only 4 bolts per head on the intake, there isnt any bolt holes in the middle
lt1q4.jpg



lt1q5.jpg


http://www.corvetteactioncenter.com/specs/c4/1996/lt1lt4.html

http://www.grumpysperformance.com/sept2017/lt1vsgen1.jpg
http://www.grumpysperformance.com/april2017/lt1q6a.jpg


http://www.grumpysperformance.com/april2017/lt1q7.jpg

http://www.grumpysperformance.com/april2017/lt1q8.jpg

[IMG]http://www.grumpysperformance.com/april2017/lt1q9.jpg

the later GEN2 LT!/LT4 reverse coolant flow block (ABOVE) differs from the first gen SBC
the LT1/LT4 second gen SBC engine was standard in the 1992-1996 corvette
Lt1_block.gif


look carefully at the first gen SBC block below
350blockla.jpg


http://garage.grumpysperformance.co...ts-differences-useful-links.13141/#post-68540


http://garage.grumpysperformance.co...ts-differences-useful-links.13141/#post-68540

https://corvetteparts.com/item/engine-cooling-system-rubber-hose-set-lt1-lt4-1995-1996

1995-96 corvette cooling hoses
9EOGbQTvXcqcvnctPS9XwA_3.jpg

vZWP9szgAxyLpM5PJRVDMA_3.jpg

BTW heres some common LT1 part numbers


Ignition:
1993-1994 optispark (non-vented style, spline driven) 10457702
1995-1997 optispark (vented style, cam dowel driven) 1104032
1995-1997 vented optispark vacuum hoses 12555323
1993-1994 optispark electrical harness 12106559
1995-1997 optispark electrical harness 12130319
1993 ignition coil 1115315
1994-1995 ignition coil 10477208
1996-1997 ignition coil 10489421
1993 ignition control module 10483131
1994-1995 ignition control module 10483139
1996-1997 ignition control module 10482803

Camshaft/Valvetrain LT4 valve springs (set of 16) 12495494
LT4 Valve spring (1) 12551483
LT4 extreme duty timing set 12370835
LT4 Hotcam
(CRANE CAMS USED TO SUPPLY MANY G.M.PERFORMANCE CAMS,
this is no longer true and QUALITY has dropped off noticeably by who ever is currently supplying the cams)
LT4 1.6 roller rocker arm (1) 12557779
1993-1994 front cover (includes round seals) 12551636
1995 front cover (includes round seals) 12552426
1996-1997 front cover (includes round seals) 12552427
1993-1994 front cover opti seal 10128317
1995-1997 front cover opti seal 12552428
1993-1997 front cover crank seal 10128316
1993-1997 front cover water pump seal 10217886
1993-1997 front cover gasket 10128293

General Engine:
LT4 heads 12555332
LT4 Intake Manifold 12550630

Misc
F-body a/c delete pulley 10115875
1993-1997 water pump 12527741
1993-1997 water pump coupling 10128334
1993-1994 1LE intake elbow (no vent hole for opti) 25147210
1995-1997 1LE intake elbow (for vented opti) 25147187
1994-1997 front flexible fuel supply lines 10258441

PCM Related
1993-1995 knock sensor 10456126
1996-1997 knock sensor 10456287
LT1 Knock Module 94-95 OBD1 16217700
LT1 Knock Module 96-97 OBD2 16214661
LT4 Knock Module 96-97 OBD2 16214681

Head Gasket Thickness
Stock gasket = 0.040
Fel Pro 1074 = 0.039
Impala = 0.029
Mr Gasket 5716 = 0.026

12561388 Main Bearing Cap Bolt Outer 10
3877669 Main Bearing Cap Bolt Inner 6
12561389 Main Bearing Cap Stud Inner 3
9442946 Main Bearing Cap Nut For Windage Tray 1
12453170 Camshaft Bearing—Camshaft #1 1
12453171 Camshaft Bearing—Camshaft #2 1
12453172 Camshaft Bearing—Camshaft #3, 4 2
10241154 Camshaft Plug—Rear 1
88891749 Freeze Plug, Cup—Brass 41.1mm 8
10120990 Main Bearing (Std) #1, 2, 3, 4 (All Small Blocks Except 383) 4
10120993 Main Bearing (Std) Rear (All Small Blocks Except 383) 1
1453658 Transmission Dowel Pin 5/8″ X 1 3/16″ 2
12554553 Front Dowelpin 1/4″ X 5/8″ 2
585927 Dowel Pin 5/16″ X 9/16″ 4
14081701 1/4″ Pipe Plug (Thread Socket Head) 4
14091563 Oil Galley, Steel Cup Plug (.476″) 4
9441003 Rear Seal Housing Locator Pin 7/16″ X 9/16″ 1
14084945 Block Drain Plug (1/4-18 X .56) Threaded 2
14088556 Rear Seal Retainer 1
10088158 Rear Crank Seal 1-Pc Style 1
14080362 Oil Pan Stud—Outboard 1
12555771 Rear Adapter Gasket to Block 1
14101058 Adapter Stud 2
14088561 Adapter Bolt—Torx Upper 1
9439915 Hex Nut, Adapter To Stud 1/4-20 X .234 1
14088562 Adapter Bolt, Torx Thru Loc Pin 1/4-20 X .75
10121044 Rear Seal (2-Piece Seal Design) 1
12513961 Front Cover, Sheet Metal With Welded Pointer 1
10108435 Front Cover Gasket—Sheet Metal Cover 1
10243247 Front Crank Seal—Sheet Metal Cover 1
12562818 Cover, Engine Front w/o Pointer ZZ4 Design Engines 1
10228655 Front Crank Seal 1
9439930 Front Cover Bolt 10
10213293 Front Cover Bolt 6
12551135 Front Cover Bolt 2
10213294 Eng Frt Cover Bolt Grommet 8
14090911 Plug (3/8-18 Threaded) ar
10168527 Head Bolt—Short 4
10168526 Head Head—Medium 20
10168525 Head Head—Long 4
10089648 Rocker Arm—w/Nut & Ball (Use With All Steel Rockers) ar
10088128 Camamsft Retainer 1st Des 3.620 Bolt Pattern 1
10168501 Camshaft Retainer 2nd Des 3.294 Bolt Pattern 1
14093637 Camshaft Bolt Retainer (Torx) 2
12554553 Camshaft Sprocket Locator Pin To Cam 1/4 X 5/8 1
9424877 Camshaft Bolt Sprocket 5/16-18 X 3/4 300m 3
10108688 Connecting Rod—All Except 383 Engines ar
461372 Connecting Rod Bolt—All Except 383 Engines ar
225854 Connecting Rod Nut—All Except 383 Engines ar
12523924 Connecting Rod Bearing (Std) Except 383 Engine ar
10046031 Flywheel Locator Pin 7/16 X 7/8 1
14061685 Clutch Pilot Bearing All With Manual Trans. 1
106751 Damper Key—Front Of Crankshaft (Woodruff) 1
3754587 Water Pump Gasket 2
9442012 Water Pump Bolts 3/8-16/ 2 1/4 4
14088753 Water Outlet 1
10198997 Water Outlet Bolts 2
10105135 Water Outlet Gasket 1
10207373 Thermostat, 195 Deg 1
10202456 Thermostat, 180 Deg 1
10108676 Oil Pan Gasket (1-Pc Des) 1
11518377 Oil Pan Drain Plug 12mm 1
3536966 Oil Pan Drain Plug O-ring Seal 1
3921988 Oil Pan Drain Plug, 1/2 1
14090908 Oil Pan Drain Plug Gasket 1
12553058 Oil Pan Reinforcement LH 1
12553059 Oil Pan Reinforcement RH 1
9440033 Oil Pan Bolt 1/4-20 X 5/8 14
12338130 Oil Pan Nut 5/16-18 2
9424877 Oil Pan Bolt 5/16-18 X 3/4 2
12551154 Oil Tube Indicator 1
12551144 Oil Tube Indicator 1
3952301 Oil Filter Adapter w/Bypass Valve
3951644 Oil Filter Adapter Bolt 5/16-18 X 1 1/8 2
3764554 Oil Pump Shaft Retainer (Nylon) 1
12525810 Intake Manifold Gaskert Set (For ZZ4 Engines) 1
89017465 Intake Manifold Gasket (For Vortec Design Heads) 1
12550027 Bolt, Intake Manifold (All With Vortec Design Heads) 8
88891769 Bolt, Intake (3/8-16 X 1 1/2 ) ZZ4 Design Engines 4
14091544 Bolt, Intake (3/8-16 X 1 1/8 ) ZZ4 Design Engines 4
9439918 Bolt, Intake (3/8-16 X 1 3/8 ) ZZ4 Design Engines 4
6269414 Manifold, Egr Cover, ZZ4 Engine 1
12554530 EGR Gasket ZZ4 Engine 1
9442184 EGR Cover Bolt T/w 9439571 Washer 2
14094792 Manifold, Choke Cover ZZ4 Engine 1
14096848 Manifold Choke Cover Gasket ZZ4 Engine 1
14094069 Fuel Pump Block Off Plate 1
12560223 Fuel Pump Cover Gasket 1
3719599 Fuel Pump Adapter Plate 1
9440033 Bolts, Fuel Pump 1/4-20 X 5/8 2
9442963 Bolts, Fuel Pump 3/8-16 X .3/4 2
3704817 Fuel Pump Push Rod 1

Last edited: Jun 10, 2017



more info

http://www.nookandtranny.com/Info_LT1.html

lt1 cylinder heads don,t flow coolant thru the intake to the radiator like the earlier heads do, the water pump is the exit point for coolant flow.


the lt1 heads will bolt on, too a standard sbc block, coolant passages are not an exact match, and theres no coolant ports in the LT1 heads too feed coolant too the intake manifold and radiator
theres no coolant flowing through the LT1/LT4 intake manifold, so you can,t bolt the standard SBC intake too the LT1 heads and get coolant flow back too the radiator, you can,t bolt an LT1 water pump too an earlier first gen SBC as the block and way the pump is driven is totally different, the LT1 water pump is driven bye a camshaft splined drive


http://www.enginebuildermag.com/1999/09/rebuilding-the-chevrolet-lt1-engine-2/

http://garage.grumpysperformance.com/index.php?threads/lt1-cooling-info.2538/

LT1 HEADS
p34413_image_large.jpg

theres no coolant flowing through the LT1/LT4 intake manifold, so you can,t bolt the standard SBC intake too the heads and get coolant flow back too the radiator, the LT1 water pump is driven bye a camshaft splined drive
lt1eg.jpg


lt1coold.jpg


LT1 water pump
lt1_water_pumps.jpg

NOTICE THE STANDARD DESIGN HEADS HAVE WATER to INTAKE TRANSFER PORTS
SBC.gif


INFO BELOW FROM
http://www.indipalass.com/ARCHIVE/TechC ... System.htm

http://automotivemileposts.com/autobrev ... ecoil.html

"LT1 Reverse Flow Cooling System
By Scott Mueller.

One of the greatest features of the '92 and up Chevrolet LT1 engine is the reverse flow cooling system. In fact it is reverse flow cooling that is truly the key to the incredible performance of the modern LT1. Reverse flow cooling is vastly superior to the conventional cooling systems used on virtually all other engines. This is because it cools the cylinder heads first, preventing detonation and allowing for a much higher compression ratio and more spark advance on a given grade of gasoline. A fringe benefit is that cylinder bore temperatures are higher and more uniform, which reduces piston ring friction. Because of this new cooling system, the LT1 can easily meet ever increasing emissions standards with significant gains in power, durability, and reliability.

Conventional Coolant Flow:

In a conventional engine design, coolant enters the front of the block and circulates through the block's water jacket. The coolant is first heated by the cylinder barrels, and then hot coolant is subsequently routed through the cylinder heads and intake manifold before returning through the thermostat to the radiator.

Because the coolant from the radiator is first directed to the cylinder bores, they run at below optimum temperatures which increases piston ring friction. The heads subsequently get coolant that has already been heated by the cylinder block, which causes the heads to run well above optimum temperatures. The hotter cylinder heads promote detonation (spark knock) and head gasket failures. To combat the increased tendency to detonate, compression ratios has to be lowered and spark advance reduced, which significantly reduces engine power output and efficiency.

Besides promoting detonation, causing gasket failures, forcing reduced compression, spark advance, and significantly reduced power output, a conventional cooling system causes several other problems. Since the thermostat is on the exit side of the system, it does not have direct control over the cold coolant entering from the radiator. This is especially true when the thermostat first opens after reaching operating temperature. As the thermostat first opens allowing hot coolant to exit the engine, a rush of very cold coolant enters the block all at once, shocking the engine and causing sudden dimensional changes in the metal components. The extreme thermal shock experienced by the engine causes head gaskets and other soft parts to fail much more quickly.

Conventional cooling system design also allows isolated engine hot spots to occur, which lead to the generation of steam pockets and coolant foaming. Coolant which is full of air and foam reduces cooling system performance and can even lead to engine overheating.

LT1 Coolant Flow:

The LT1 is completely different since it uses reverse flow cooling. The incoming coolant first encounters the thermostat, which now acts both on the inlet and outlet sides of the system. Depending on the engine coolant temperature, cold coolant from the radiator is carefully metered into the engine. This allows a more controlled amount of cold coolant to enter, which immediately mixes with the bypass coolant already flowing. This virtually eliminates the thermal shock present in the old system.

After entering through one side of the 2-way thermostat (at the appropriate temperature), the cold coolant is routed directly to the cylinder heads first, where the combustion chambers, spark plugs and exhaust ports are cooled. Then the heated coolant returns to the engine block and circulates around the cylinder barrels. The hot coolant from the block re-enters the water pump, and hits the other side of the 2-way thermostat, where it is either re-circulated back through the engine or directed to the radiator, depending on temperature.

The main concept behind reverse flow cooling is to cool the heads first, which greatly reduces the tendency for detonation, and is the primary reason that the LT1 can run 10.5 to 1 compression and fairly significant ignition advance on modern lead-free gasoline. Reverse flow cooling is THE KEY to the Generation II LT1s increased power, durability, and reliability over the first generation smallblock engine.

Thermostats:

All LT1 engines utilize a special 2-way acting full bypass thermostat. This means that the thermostat regulates coolant flow both in to as well as out of the engine, while the bypass portion of the thermostat circuit supplies the water pump with a full flow of liquid coolant at all times. This is unlike a conventional engine thermostat, which only regulates coolant flow at the engine outlet, and which does not allow full flow through the water pump when the engine is cold and the thermostat is in bypass mode.

Both sides of the 2-way thermostat used in the LT1 are linked together, and a single wax pellet actuator operates the spring loaded mechanism at a pre-set temperature. When the designated temperature is reached, the wax pellet expands, opening the dual acting valve. All current LT1s come from the factory with a relatively low 180 degree temperature thermostat. Most conventional engines today use 195 degree thermostats in order to meet emissions specifications at the expense of power, durability, and reliability.

It is important to note that the 2-way thermostat is unique to the Generation II LT1 and is not interchangeable with older Chevrolet smallblock engines. This is particularly important if you decide to change to a colder 160 degree thermostat, make sure it is the proper dual acting type required by the modern LT1.

Additional LT1 Cooling System Improvements:

In addition to reverse coolant flow, there are several other improvements in the LT1 cooling system over conventional engines.

Dry Intake Manifold:

The LT1 has absolutely NO water running through the intake manifold! Conventional cooling systems have passages in the intake manifold which allow coolant to crossover from one side of the engine to the other. In the LT1, coolant crossover occurs in the water pump, which is also where the thermostat is located. Since there are no coolant passages in the intake manifold, a major source of leaks has been eliminated. Overall engine reliability is improved since an intake manifold leak allows coolant to enter the top of the engine which can quickly wipe out the camshaft, lifters, and other major engine components. Designing a dry intake manifold without either coolant passages or a thermostat housing also allows a much lower profile. The LT1 engine is 87mm (nearly 3.5 inches) lower than the previous L98 Corvette engine.

Gear Driven Water Pump:

One big problem with conventional cooling systems is the water pump, which simply cannot last a targeted minimum 100,000 mile reliability figure without experiencing leaking gaskets or seal failures. This has traditionally been caused by the excessive side loads placed on the bearings and seals of a conventional water pump through the belt drive mechanism. In the LT1 this problem is solved by driving the water pump directly via a spur gear driven by the camshaft sprocket. This results in a dramatically more reliable water pump that should easily last 100,000 miles or more.

Since the water pump is no longer belt driven, the vehicle will still be driveable even if the serpentine belt fails. This is a major safety factor as it allows one to drive the partially disabled vehicle to the nearest service center.

Steam Vents:

The LT1 has strategically placed steam vents at the back of both cylinder heads. Since the heads are the hottest part of the engine, pockets of steam can be more easily generated there. The steam vents are connected together by a crossover vent tube at the back of the heads, which directs any steam and a small flow of coolant to the front of the engine where it flows through the throttle body, warming it for improved cold weather performance. After passing through the throttle body, most of the steam is condensed back into liquid coolant and returned to the system.

In LT1 B/D-cars, coolant exiting the throttle body is passed directly into a pressurized coolant reservoir where any air remaining in the coolant is completely scavenged. In LT1 F-cars, coolant from the throttle body connects to the heater outlet via a vented "tee" connector, where any trapped air in the system can be bled off manually. Eliminating steam pockets and foam in the coolant allows for more uniform cooling system performance, preventing hot spots and potential overheating.

Reverse Flow Radiator:

Unlike a conventional cooling system, the thermostat coolant outlet is connected to the bottom of the radiator. This forces the coolant entering the radiator to push up through the radiator core and eventually emerge through the top radiator coolant outlet. This helps to eliminate air pockets in the radiator, and provides a more even distribution of cooling through the core and improving radiator efficiency.

Precision Machined Thermostat Housing:

The thermostat housing is a precision machined component that fits directly onto the top of the water pump without a gasket. Instead, an O-ring is used to seal the thermostat inside the housing. This precision design reduces the tendency for leaks, plus it makes thermostat replacement a very simple job since there is no old gasket material to scrape off. Servicing is further simplified because the thermostat housing is situated directly on top of the water pump, and access is unobstructed. I dare say that the LT1 thermostat is the easiest to change I have ever experienced. Finally, an air bleeder valve is located on the top of the thermostat housing, which allows one to quickly and easily bleed out any trapped air after cooling system maintenance has been performed.

Low Operating Pressure:

The entire cooling system on the LT1 is designed to operate at lower pressures than conventional cooling systems. The maximum operating pressure in the LT1 cooling system is 15 psi for B/D-cars and 18 psi for F-cars, limited by a pressure cap. These limits are similar to other cars, but in the LT1, these maximum pressures are rarely reached. Running at a lower pressure drastically decreases the number of leaks and significantly improves overall reliability and durability.

Coolant Reservoir:

Corvette and B/D-car LT1 applications use a pressurized coolant recovery reservoir instead of a non-pressurized overflow tank used with conventional cooling systems. All of the coolant flows continuously through the pressurized reservoir, which is an integral part of the cooling system. The pressurized reservoir in the LT1 B/D-cars is connected to the cooling system in three places. One inlet hose connects to the top of the RH radiator tank, a second inlet hose is attached through a "tee" connection on the heater inlet hose, and a third outlet hose is connected to a "tee" connection in the throttle body heater outlet.

The pressurized reservoir is mounted at the highest point in the system, and provides a place where all air can be continuously scavenged from the coolant. Any steam and bubbles are allowed to rise to the surface, eliminating foam and providing pure liquid coolant back to the engine. Pure liquid coolant is returned to the system via the heater outlet hose connection. The pressure relief/vent cap in these systems is rated at 15 psi and is located on the reservoir rather than the radiator.

LT1 F-cars use a conventional coolant recovery system which consists of a non-pressurized coolant overflow tank connected to the radiator by a single hose. These cars use an 18 psi rated pressure relief/vent cap on the radiator like most conventional systems. Since these cars cannot scavenge air from the coolant as well as the B/D-car or Corvette systems, they have two air bleeder valves for manually bleeding trapped air from the system. One is in the thermostat housing, which is the same as all other LT1 engine vehicles, and the second one is located in a "tee" where the coolant from the throttle body connects to the heater return hose.

B/D-car LT1 (Caprice/Impala/Roadmaster/Fleetwood) Cooling Systems:

Standard equipment for all LT1 equipped B/D-cars is a dual electric fan setup with a 150-watt primary (RH) fan and a 100-watt secondary (LH) fan. The electric engine coolant fans are independently operated by the PCM (Powertrain Control Module) based on the inputs from the Engine Coolant Temperature (ECT) sensor, A/C Pressure Sensor, Vehicle Speed Sensor (VSS), and various other inputs.

The B/D-car coolant fans operate under PCM control at the following engine temperatures and A/C system pressures:

Fan Mode
Temperature A/C Pressure
Primary (RH) Fan ON 107 C 225 F 189 psi
Primary (RH) Fan OFF 103 C 217 F 150 psi
Secondary (LH) Fan ON 111 C 232 F 240 psi
Secondary (LH) Fan OFF 107 C 225 F 210 psi

Additionally, the PCM will turn off the fans at higher vehicle speeds (above 48 MPH I believe) since running fans can actually impede airflow through the radiator at high
speed. Each fan also has a minimum running time. Once activated, the primary fan will run for a minimum of 50 seconds, and the secondary fan for a minimum of 26
seconds. Finally, certain Diagnostic Trouble Codes (DTCs) may cause the PCM to turn on one or both fans.

All LT1 B/D-cars have two transmission oil coolers and an engine oil cooler as standard equipment. The transmission coolers include a primary oil to water type inside the RH radiator tank, and a secondary external oil to air cooler (KD1) mounted in front of the radiator on the RH side. The external KD1 cooler is an aluminum stacked plate type cooler painted black with metal tube lines linking it in series with the other cooler in the radiator tank. LT1 B/D-cars also include an engine oil to water cooler (KC4) mounted in the LH radiator tank.

Optional B/D-car LT1 Cooling Systems:

There are two optional cooling system upgrades for LT1 B/D-cars, called V03 (Extra Capacity Cooling), and V08 (Heavy Duty Cooling). Performance models such as the WX3 (Impala SS) and 9C1 (Police) cars automatically get the upgraded V03 (Extra Capacity Cooling) system. V03 includes a larger radiator, an increased capacity A/C condenser, and an upgraded secondary electric fan. V03 is also optional on most B/D-car models.

Note that the '94 V03 (Extra Capacity Cooling) option uses a 150-watt primary (RH) fan, and an upgraded 240-watt secondary (LH) fan. In '95-'96 the V03 package was revised and no longer included an upgraded 240-watt secondary fan. Instead the standard 100-watt secondary fan was used, which is the same as the base cooling system.

B/D-cars other than the Impala SS or Police package Caprice also have an optional V08 (Heavy Duty Cooling) package which is part of the V92 (Trailer Towing) package. V08 includes the larger radiator, increased capacity A/C condenser, and upgraded secondary fan as in the V03 system, however it differs in the primary cooling fan. With V08 the 150-watt electric primary fan is replaced by a mechanical belt driven thermostatic clutch fan. To drive the mechanical fan, the V08 system includes a crank pulley, belt tensioner and bracket, and a large radiator shroud in addition to the mechanical fan itself. This package is not available on the WX3 (Impala SS) or 9C1 (Police) cars since the mechanical fan is driven by an additional pulley and belt on the engine crankshaft, which draws engine power thus reducing performance.

The mechanical fan used with the V08 cooling system contains a built-in thermostatic clutch which senses the temperature of air that has been drawn through the radiator. When the temperature of this air is below 66 degrees C (151 degrees F), the clutch freewheels and limits the fan speed to 800-1,400 rpm. When the temperature rises above 66 degrees C (151 degrees F), the clutch begins to engage, and the fan speed increases to about 2,200 rpm. The RH radiator hose in V08 equipped vehicles has a steel tube section near the fan designed to prevent damage in case of fan contact.

There are several SEO (Special Equipment Option) B-car cooling options which are included as standard only with 9C1 (Police) package Caprices. These include the following:

In addition to the standard inclusion of the V03 (Extra Capacity Cooling) package, all LT1 Caprice 9C1 (Police) cars also include SEO 1T1 (Silicone Radiator and Heater Hoses). SEO 1T1 consists of special green radiator and heater hoses made out of pure silicone rubber. These hoses are designed to last the life of the vehicle and never need replacement unlike the standard black rubber hoses. SEO 1T1 also includes heavy duty stainless steel worm gear hose clamps which replace the standard squeeze type hose clamps. The clamps have a solid full perimeter band, which prevents the hose from extruding between the slotted area where the screw fits. This also prevents the hose from being cut or damaged by the clamp, and allows a more even sealing force around the entire clamp perimeter.

The 9C1 Police package also includes SEO 7P8 (External Engine Oil to Air Cooler). This is an unpainted aluminum stacked plate type cooler which is mounted in front of the radiator on the LH side opposite the external transmission cooler. This heavy duty engine oil cooler replaces the standard engine oil to water cooler found in the LH radiator tank of other LT1 B-cars.

Also included with the Police package is SEO 7L9 (Power Steering Fluid Cooler). This consists of a loop of metal tubing installed between the radiator lower support and the front stabilizer bar. This cooler prevents the power steering fluid from overheating in rigorous driving situations such as high speed persuit.

F-car LT1 (Camaro/Firebird) Cooling Systems:

Standard equipment for all LT1 F-cars with A/C is a dual electric fan setup with primary (LH) and secondary (RH) fans. There are two different wiring schemes used for these fans, an early design that was used in '93-'94 and a late design that has been used from mid-'94 up. Note that non-A/C F-cars have a single primary fan which operates at a fixed high speed.

In '93 and early '94 models with A/C, the two cooling fans are independently operated by the PCM (Powertrain Control Module) at a high fixed speed by using a single relay for each fan. Late '94 and newer F-car models operate both fans simultaneously in either a low or a high speed mode by using 3 relays. In low speed mode, the fans are powered in series. In high speed mode, the relays operate to power both fans in parallel, resulting in a higher speed of operation.

One way to tell which setup you have is by looking at the alternator. If an F-car is equipped with the 124 amp alternator (KG7), then the vehicle has the early design setup and the fans are operated independently. If the vehicle has the 140 amp alternator (KG9), then it also has the newer design configuration which operates the fans simultaneously in low or high speed modes.

The PCM operates the coolant fans based on input from the Engine Coolant Temperature (ECT) sensor, A/C Pressure Sensor, Vehicle Speed Sensor (VSS), and various other inputs. The F-car coolant fans operate at the following temperatures and pressures:

Fan Mode
Temperature A/C Pressure
Primary (LH) or Dual Low-speed Fan(s) ON: 108 C 226 F 248 psi*
Primary (LH) or Dual Low-speed Fan(s) OFF: 105 C 221 F 208 psi*
Secondary (RH) or Dual High-speed Fan(s) ON 113 C 235 F 248 psi
Secondary (RH) or Dual High-speed Fan(s) OFF: 110 C 230 F 208 ps

*Note - this information is probably incorrect, although it is quoted from the service manual.

Additionally, the PCM will turn off the fans at higher vehicle speeds (above 70 MPH I believe) since running fans can actually impede airflow through the radiator at high speed. Each fan or fan mode has a minimum running time. Once activated, the primary fan or dual low-speed fans will run for a minimum of 50 seconds, and the secondary or dual high-speed fans for a minimum of 30 seconds. Finally, certain Diagnostic Trouble Codes (DTCs) may cause the PCM to turn on one or both fans.

All LT1 F-cars with automatic transmissions also have a transmission oil cooler as standard equipment. The transmission cooler is an oil to water type mounted inside the RH radiator tank.

Optional F-car LT1 Cooling Systems:

There is only one option in an LT1 F-car with respect to cooling, and that is an engine oil cooler (KC4). The engine oil cooler is an oil to water design that is mounted in the LH radiator tank. The KC4 oil cooler is included with various other combinations of options on the F-cars.

Operating Characteristics and Observations:

I have an accurate digital temperature gauge installed in the RH cylinder head water jacket on my '94 Impala SS. I installed a brass "T" fitting in the RH cylinder head, in the tapped hole where the factory temperature gauge sender was originally installed. This allowed me to install both the original analog gauge sender as well as the sender for the new digital gauge. With the stock 180 degree thermostat, cruising at 80 mph on a cool night I would routinely measure coolant temperatures in the head as low as 167 degrees! If I slowed down, the temperature would climb up into the 170-180 degree range depending on ambient temperatures and cruising speed. The temperature would run in the 180s-190s cruising more slowly on a hot summer day. In heavy stop and go traffic, the temperature would quickly climb up into the 220-230 degree area, which is where the primary fan starts to come on.

Many have noticed as I have that the engine will actually run cooler in traffic with the A/C on. This is because turning on the A/C will also cause the PCM to activate at least the primary fan, and possibly the secondary fan (depending on A/C system pressure) as well.

The radiator and A/C condenser in B/D-cars equipped with the RPO (Regular Production Option) V08 (Heavy Duty Cooling) or V03 (Extra Capacity Cooling) systems are extremely large, perhaps the largest of any passenger car on the market today. The cooling and A/C system performance on these cars are outstanding, in fact the best I have seen on any vehicle.

Recommendations for Cooling System improvements:

If you have a B/D-car, there are several easy improvements you can make by simply adding the cooling related SEOs (Special Equipment Options) from the 9C1 Caprice Police package. For example, I have installed all of the Police package cooling upgrades in my '94 Impala SS. This includes the 1T1 silicone hoses, 7L9 power steering fluid cooler, and 7P8 external engine oil cooler. Combined with the already powerful V03 cooling system, these factory upgrades combine to form the most extreme duty factory cooling system present on any automobile I have seen.

If you have an F-car which was not factory equipped with the optional KC4 engine oil cooler, then I would highly recommend installing it as an upgrade. The KC4 option consists of a different radiator with the engine oil cooler located inside the LH tank. An adapter installs on the oil filter pad between the filter and the engine, and lines run to the cooler in the radiator tank.

There are two other cooling system improvements that can be applied to any vehicles with the LT1 engine, including the Corvette and F-cars (Camaro/Firebird). These are to change to a colder 160 degree thermostat (180 is standard), and to alter the electric cooling fans to come on at a lower temperature. This latter function can be accomplished by adding an external thermostatic switch to the fan circuit, or by re-programming the PCM fan operation settings.

As mentioned earlier in this article, the stock fans do not come on until at least 225 degrees, which I feel is too hot. To prevent the engine from heating up this high in traffic or while moving slowly, I installed a 203 degree GM thermostatic switch (p/n 3053190) in a pre-existing tapped hole in the LH cylinder head water jacket, and wired it to both the primary and secondary fan relay via a 3-position toggle switch.

When the coolant temperature reaches 203 degrees, the primary or secondary fan (depending on the setting of the toggle switch) will run. This prevents the engine from running hotter than about 200 degrees or so. I have tested this modification in 100 degree ambient temperatures, while trapped in stop and go traffic, and never saw coolant temperatures higher than 205 degrees. I wired the toggle switch to operate either the primary or secondary fan, as well as to disconnect the thermostatic switch from the circuit, thus disabling this function. No matter what the toggle switch setting, the PCM still has control over the fan relays, and will continue to operate the fans oblivious to the additional thermostatic switch function.

I have more recently purchased the Hypertech Power Programmer, which re-programs the PCM to turn the primary fan on at 176 degrees (instead of 225), and the secondary fan on at 191 (instead of 232). At first I installed the Hypertech program without the recommended 160 degree thermostat in order to observe the operation of the fans. I found that the primary fan would run continuously once the engine had warmed up, and even the secondary fan would be on most of the time. This is due to the overlap between the high thermostat setting and the lower fan activation temperatures programmed in by Hypertech. The new settings were turning the primary fan on at a setting lower than the thermostat itself would open.

After installing the recommended 160 degree thermostat, the fans worked normally, and would only begin to run after the car was not moving which allowed the temperature to rise. In actual operation I saw temperatures while moving about 10 degrees lower than what I observed with the 180 degree thermostat. While moving very slowly or sitting stationery, the engine would never climb above the low 190 range, no matter how high the ambient temperatures was or how slow I was moving. After observing this operation, I would wholeheartedly recommend the 160 degree thermostat and the Hypertech Power Programmer. If you use the Power Programmer, then the 160 degree thermostat MUST be installed or the fans will run continuously, which is not good for either the fans, alternator, or battery.

If you do not want to purchase the (fairly expensive) Power Programmer, then I highly recommend installing the 203 degree thermostatic fan switch I listed, which will prevent the excessive temperatures encountered in traffic that are allowed by the stock PCM program settings. The fan switch will work well with either the stock 180 degree thermostat or a 160 degree unit, and will limit the maximum coolant temperatures to 205 degrees or less.

GM Vehicles Featuring the Generation II LT1:
Chassis Models Years
Y-car Corvette '92-'96
F-car Camaro/Firebird '93-'96
B-car Caprice/Impala/Roadmaster 94-'96
D-car Fleetwood '94-'96"
 
Last edited by a moderator:

grumpyvette

Administrator
Staff member
Re: LT1 & l98 cooling info
READ ALL THE LINKS AND SUB LINKS


Straight from the Helm GM Electrical Diagnosis Service Manual Supplement:

COOLANT FAN TROUBLESHOOTING HINTS
http://www.ebay.com/itm/1995-1996-C...diator-Hose-Set-LT1-LT4-engines-/121925824251

https://corvetteparts.com/item/heat...o-lower-heater-core-lt1-lt4-engines-1993-1996

http://garage.grumpysperformance.co...-engine-parts-differences-useful-links.13141/

Try the following checks before doing the System Check:

1. Visually check the C. FAN fuse.
2. If the Coolant Fan runs with the Ignition Switch off, replace the Coolant Fan Relay.
3. If the Auxiliary Coolant Fan runs with the Igniton Switch off, replace the Auxiliary Coolant Fan Relay.

SYSTEM CHECK

Action: With the ambient temperature above 60° and the engine cold and idling, move A/C Function Selector to NORM (if equipped with A/C).
Normal Result: Coolant fan should start after a short period.
Elec_Fan_Wiring_Diagram_-_dual_switch.JPG

cooling_fan.jpg

fr935.jpg

http://www.mamotorworks.com/corvette-c4 ... 8-935.html

Action: Move A/C Function Selector to OFF.
Normal Result: Coolant fan turns off.

Action: With the engine warmed up, run it for at a fast idle for several minutes.
Normal Result: Coolant fan turns on before Auxiliary Coolant Fan (if equipped) and before Coolant Temperature Indicator comes on.

AUXILIARY COOLANT FAN DOES NOT TURN ON (Table 1)

Connect: FUSED JUMPER
At: COOLANT FAN TEMPERATURE SWITCH CONNECTOR (Disconnected)
Condition: Ignition Switch: RUN
Connect between: DK GRN/WHT & Ground
Correct Result: Auxiliary Coolant Fan runs.
For Diagnosis: Leave fused jumper connected and go to Table 2.

* If fan runs, replace Coolant Fan Temperature switch.

AUXILIARY COOLANT FAN DOES NOT TURN ON (Table 2)

Connect: TEST LAMP
At: AUXILIARY COOLANT FAN RELAY CONNECTOR (Disconnected)
Conditions: Ignition Switch: RUN, Fused Jumper from Table 1 still in place.

Connect Between: C (DK BLU) & Ground
Correct Result: Lamp lights.
For Diagnosis: Check C. FAN Fuse and DK BLU (351) wire for an open.

Connect Between: C (DK BLU) & B (DK GRN/WHT)
Correct Result: Lamp lights.
For Diagnosis: Check DK GRN/WHT (335) wire for an open.

Connect Between: E (RED) & Ground
Correct Result: Lamp lights.
For Diagnosis: Check Fusible Link E and RED (2) wire for an open.

* If all above results are correct, go to Table 3.

AUXILIARY COOLANT FAN DOES NOT TURN ON (Table 3)

Connect: 20 AMP FUSED JUMPER
At: AUXILIARY COOLANT FAN RELAY CONNECTOR (Disconnected)

Connect Between: E (RED) & A (BLK/RED)
Correct Result: Auxiliary Coolant Fan runs.
For Diagnosis: Leave Fused Jumper connected and go to Table 4.

* If result is correct, replace the Auxiliary Coolant Fan Relay.

AUXILIARY COOLANT FAN DOES NOT TURN ON (Table 4)

Connect: TEST LAMP
At: AUXILIARY COOLANT FAN MOTOR CONNECTOR (Disconnected)
Condition: Fused Jumper from Table 3 still in place.

Connect Between: B (BLK/RED) & Ground
Correct Result: Lamp lights.
For Diagnosis: Check BLK/RED (903) wire for an open.

Connect Between: B (BLK/RED) & A (BLK)
Correct Result: Lamp lights.
For Diagnosis: Check BLK (151) wire for an open.

* If result is correct, replace the Auxiliary Coolant Fan Motor.
 
Last edited by a moderator:

grumpyvette

Administrator
Staff member
#
http://shbox.com/1/4th_gen_tech2.html

Cooling System Operation and Testing

http://www.aa1car.com/library/electric_cooling_fan.htm

http://www.aa1car.com/library/cooling_f ... oblems.htm

http://www.aa1car.com/library/coolant_sensors.htm

http://www.aa1car.com/library/overheat.htm

http://www.aa1car.com/library/air_temp_sensors.htm

Electric cooling fans attached to the radiator keep the LT1 from overheating when there is little or no air passing through the radiator core (car going very slow or stopped and engine running). It is normal for the temps on the gauge to go up to the middle or past middle of the gauge before the fans kick on. The middle of the gauge is in the range of 210º - 220º. With factory programming, the PCM will command low speed fans (or primary fan) "ON" at 226º and "OFF" at 221º and high speed fans (or secondary fan) "ON" at 235º and "OFF" at 230º. The fans should come on before it gets to any part of the red zone. (see "dual fan configuration" below about primary and secondary fans)
The f-body LT1 uses a 180° thermostat as stock.

The PCM gets it's temp readings from a sensor that is in the water pump. If the reading the PCM receives is inaccurate, the fans may not come on at the correct time. The PCM also uses this temperature for lookup in fuel calculation tables. If there is a problem that causes the reading to be always low (cold), the PCM will add extra fuel. This can cause hard starting when warm and an overly rich condition when running.

The gauge gets it's information from a sensor that is in the driver's side head. Inaccurate gauge readings can be from this sensor or it's wiring (the wire burned on a header pipe is common). The temp that the PCM sees can be monitored with a scan tool and compared to the gauge reading. They should be close, but don't expect them to be "perfectly" synchronized.

The fans are programmed to come on when the a/c is turned on. A/c Pressure monitoring sensors feed the PCM info and depending on the situation, the PCM may command the fans off for brief periods. Also, when the car reaches sustained higher speeds, the fans may be commanded off so incoming air can flow through the radiator unimpeded and provide the cooling needed.

Fans will also come on when the SES lamp comes on. The PCM does this when certain (most) DTCs are detected to protect the engine from a situation where it may overheat.


There are two versions of the dual fan configuration:

# 1993-1994 - Primary and Secondary fans that operate at only one speed. When initially commanded on, only the primary fan (driver side) comes on. It operates alone at full speed. If the temp threshold is met for addtional cooling, the secondary fan (passenger side) also is commanded on. At this point, both fans are running at full speed.
These fans use a two relay architecture that can be seen in the fuse/relay panel that is under the hood.

# In late 1994 and into 1995, there was a change to low and high speed fans. When initially commanded on, both fans will come on at a low speed. When the high speed temp threshold is met, they both bump up to high speed. A three relay architecture is used for this fan version (seen in the fuse/relay panel). By adding a third relay, low speed can be achieved by running the power to the fans in series. This way, each fan does not get full voltage and runs at a slower speed. High speed happens when the relays switch to provide full voltage to both fans. Low speed is less noisy and should result in greater fan longevity. High speed is not always needed.


2 Relay System PCM Commanded Fan Operation PCM Wire Color Grounded Fan Operation Relay Operated
#1 #2 #3
Primary@226º Drk Grn @A11 Primary (LH) fan full speed X - n/a
Secondary@235º Drk Blu @A10 Secondary (RH) fan full speed X X n/a
3 Relay System Low Speed@226º Drk Grn @A11 Low Speed (both fans) X - -
High Speed@235º Drk Blu @A10 High Speed (both fans) X X X
For both fans to operate in either system, both relay leads must be grounded. Grounding only the Drk Blu wire will result in only the RH fan operating at high speed.



Here are some fairly simple things to check for various complaints:

~Fans are not operational at any time~


# Check fan fuses in the underhood fuse/relay panel
# Check fan relays (same location). Aside from getting out any electrical equipment to test the relay, you can swap it with another one (such as the fog lamp relay) and test for function. See if the relay works for the fog lamps and/or the swapped-in relay makes your fans work. Nearly all the relays in the panel are the same, except for maybe the ABS relay.
# You can jumper two pins on the DLC that should cause the fans to come on. 1993-1994 cars with the 12 pin DLC can jumper pins A and B. On a 1993, that is the same way that you would retrieve trouble codes from the ecm. The 1994 won't give you any codes, but the fans will engage. 1995-1997 uses pins 5 and 6 on the 16 pin DLC to initiate what is called "field service enable mode". That will cause the fans to come on and operate most sensors for sanity checking. After placing the jumper on the correct pins, turn the key to ON (don't start). If the fans work after jumpering the DLC, your PCM is capable of operating the fans and all fan wiring/relays should be ok.
# Deeper problems can be solved through testing and using the wiring schematic.


~Fans don't come on except when the a/c or SES is on~

~Temp gauge continues to rise with no automatic fan operation~


# With a scan tool, check to see what temp the PCM is seeing from the sensor in the water pump. Make sure you are aware of the temps the fans come on (stated in the beginning of this article). If the temp it sees is incorrectly low, it won't know to turn the fans on. Another possibility is that the temp is really ok, but the gauge is reading wrong. That is why you need to use the scan tool to see and compare the readings. Info on testing wiring and sensor can be found here.
# If that looks ok, then your PCM may have issues. You could always try resetting the PCM by pulling the PCM BAT fuse for about 30 seconds.

Testing the ECT (Engine Temperature) Sensors and Connections

fan1schematic_1995.jpg


ECT Temperature vs. Resistance Values

ºC ºF Ohms
100 212 177
90 194 241
80 176 332
70 158 467
60 140 667
50 122 973
45 113 1188
40 104 1459
35 95 1802
30 86 2238
25 77 2796
20 68 3520
15 59 4450
10 50 5670
5 41 7280
0 32 9420
-5 23 12300
-10 14 16180
-15 5 21450
-20 -4 28680
-30 -22 52700
-40 -40 100700

Use a Digital Volt Meter (DVM) set to ohms to measure resistance. Note: Use a high impedance meter (at least 10 megohm) when dealing with the PCM. Most modern DVMs will do, but your old analog meter can damage the PCM. It is also a good idea to get a " reference" from the meter you are working with. With the DVM on the ohms scale, touch the two meter leads together and note the ohm reading. It may not always be perfectly zero, but may be within a tenth or two. Now when you take an ohm reading, you will know what the meter will show when there is really no resistance.

* The sensor in the head has only one terminal. This sensor is for the temperature indicator on the dashboard. Place one test lead on the sensor terminal and the other on a known good ground. Compare the reading to the table. If your car is cold from sitting overnight, the reading should be close to ambient temperature.
* The sensor in the water pump has two terminals. This sensor is for the temperature input to the PCM. Place a test lead on each of the sensor terminals to take the reading. (When reading resistance, it does not matter which lead goes to which terminal)

If the sensor seems to be ok, you may also need to test at the harness connector for proper lead conditions. Use your test meter set on the dc voltage scale to do this. You will need the key in the RUN position, but don't have to start the car.

* For the one lead connector at the head, place the red test lead on the connector terminal and the black test lead to a known good ground. With the key ON, you should read battery voltage (+12vdc or close to it). You can also ground the lead and see if the gauge in the car deflects to full hot.
o If you get no voltage, switch the meter to ohms to see if the lead is grounded.
o No voltage or no ground mean that the lead is open.
o If the gauge is at full hot all the tme, the lead is grounded back toward the gauge. It could be possible for the lead to be pinched and grounded toward the gauge and broken and open back toward the sensor (like in the case of the wire getting caught somewhere during some major engine work). Physically tracing the wire from the sensor into the harness should locate the problem.
* The two lead connector at the water pump has a black (ground) lead and a PCM +5vdc power lead (probably yellow). Place the black meter test lead to black connector lead and the red meter test lead to the other connector lead (yellow on my 1995). You should read +5vdc because this is monitoring voltage being supplied from the PCM.
* If you get no reading:
o Test the yellow lead by placing the DVM red lead on it and the DVM black lead to ground. A +5vdc reading will indicate the lead is ok.
+ If you get no voltage, switch the meter to ohms to see if the lead is grounded.
+ No voltage or no ground mean that the lead is open.
o You can test the black connector lead by using the ohms scale on the DVM. Place the DVM black lead to ground. Place the DVM red lead to the black lead of the connector. If the lead is ok, you will get an ohm reading close to zero. If you get no reading or a very high one, the lead is open or partially open.
* OBD-I DTCs 14 and 15 or OBD-II DTCs P0117 and P0118 are typically associated with problems the PCM sees with the sensors or circuits.

Footnote: If you ever have to test the IAT, it operates the same as the two lead coolant sensor. The same temp vs. resistance table above is applicable to the IAT, as well as the +5vdc lead and ground wire at the harness connector.
 

grumpyvette

Administrator
Staff member
oil flow, not coolant does the first heat transfer from the critical bearings,rings,rockers,springs,ETC. oil flow must remain constant and under enought pressure to always provide a film between the moving metal parts, a high capacity oil pan in the 7qt-9qt range and windage control system for the oil helps a great deal with engine cooling.
I have repeatedly said that your oil temp should keep above 215° to allow moisture to burnout of the oil and that your coolant temp should stay in the 180-220 range
SMOKEY YUNICK, in several places in several books, refers to extensive dyno testing he did for General Motors, where they consistently found, that both engine wear and hp production benefited when the oil temp stayed above 215° but below 240°, and the coolant temperature stayed between 180 and 220, degrees, or as SMOKEY said, trying keep your oil hot, but your coolant, about 20 to 30° lower in temperature but the coolant should never be below 180°, and should not exceed 220°, while temperature should never below the below 215°, and 235 to 240 is about ideal, mineral base oils tend to start breaking down over 240°, synthetic oils can easily handle temperatures up in the 270 degree range in for extended periods, but they performed best in their lubrication in cleaning function went down in the 240 range


I normally buy oil pans from these guys as they are good quality for the money

http://www.parts123.com/PartFrame.a...stmotorsportsinc.com&TITLE=Midwest_Motorsport

http://forum.grumpysperformance.com/viewtopic.php?f=57&t=853

i don,t usually have alot of money to waste so I normally buy this #KEV 1090 oil pan for $100 and weld a sump extension forward
with this kit they sell for $26 # MWM 15900
and add a windage screen #MIL 32250 for $80,so for about $220-$245 you can have a baffled 9.5 qt oil pan with windage screen
http://www.moroso.com/catalog/categorydisplay.asp?catcode=11330
21312_inside.jpg

while I tend to build or modify my personal oil pans
MOROSO has a good product, in several versions,
21314_draw1.jpg

21314_draw2.jpg

21312_draw2.jpg

which I can recommend if your buying one!


you will need to carefully measure clearances for the cross member,suspension,headers,starter,oil filter, ground clearance, ETC. before ordering , or modifying an oil pan

restricting coolant flow speeds to help cooling is a MYTH,started when guys found that removing the thermostat could cause overheating on some cars, the thermostat did not restrict the flow significantly but it did tend to prevent the waterpump from cavitateing and failing to efficiently move coolant.
large tube aluminum radiators tend to cool very effectively

mounting an electric push fan infront of your radiator can significantly help lower temps

water wetter additive can disolve some types of paper thermostat gaskets

a 17lb radiator cap is about as high a pressure rating as you can use on a standard cooling system

air flowing over the outter surface of a road racing style, 8qt or larger extended sump oil pan removes a good amount of heat from the engine, tall valve covers can also act to radiate heat from the oil running over the inner surfaces

header coatings can also help reduce under hood temps

naca ducts or side vents that allow efficient removal of air flow behind the radiator can help cooling





YES YOU SHOULD RUN A THERMOSTAT, about 180F-190F prefered on most high performance cars


FACTORS THAT IMPEDE COOLING EFFICIENCY


1 - Coolant does not pass through radiator freely. Over time, chemical reactions can cause corrosion buildup in the radiator tubes and can restrict the flow of coolant through the radiator. Also, debris can accumulate at the tube openings (similar to a strainer) and the resulting blockage can restrict flow. The result is that the heat is not transferred from the coolant to the fins and overheating will likely occur.

2 - Air flow is restricted through the radiator and heat cannot be dispersed into the air. If trash or bugs clog the fins on the radiator, then the air flow cannot pass over the fins and the heat is not dispersed into the air. The buildup of heat can cause overheating.

3 - Deterioration. Over time, the metal fins oxidize and deteriorate. Road salt and salty air from coastal areas contribute to speeding up the oxidation process of radiator fins.

http://www.jcwhitney.com/productnoitem.jhtml?CATID=5131&BQ=jcw2
I6993.gif
I6990.gif
RADIATOR CORROSION INHIBITOR Prevents overheated radiators caused by rust, scale and corrosion. Save money on needless flushing, repairs, anti-freeze changes, special additives! Zinc anode slips in radiator filler neck and neutralizes rust/corrosion-causing chemicals. Lasts for years. NOTE: Not for radiators with plastic tanks. http://www.pjhbrands.com/vht/coppergasketcement.htm
coppergasket.jpg

http://www.radcapproducts.com/order.html" http://www.radcapproducts.com/order.html
PKG115.jpg




if you don,t read the links youll miss most of the info!

http://www.radiatorbarn.com/

http://www.streetrodstuff.com/Products/157/

http://www.streetrodstuff.com/Articles/Cooling/More_Cooling_Suggestions/

http://garage.grumpysperformance.co...leaning-trash-out-of-the-radiator-fins.11712/

http://www.streetrodstuff.com/Articles/Cooling/Cooling_Suggestions/

http://www.prenhall.com/autoweb/chekchart/classch5.pdf
 
Last edited by a moderator:

grumpyvette

Administrator
Staff member
This might help also........

Heres a article that might help by LARS GRIMSRUD
Overview
C4 Corvettes seem to have chronic overheating/run hot problems, especially after about 100,000 miles.

The radiator on a C4 ‘Vette is an aluminum and plastic, single-row unit. It is remarkably small and light, and looking at it, you just know that it can’t possibly be big enough to handle the cooling for a high performance, V8 engine…

The design of this compact radiator is right out of state-of-the-art NASCAR radiator designs: Every single little fin in the radiator is a multi-piece, serrated fin – not a solid fin like on the old “heavy duty 4-row” radiators in our old Musclecars. This makes the ‘Vette radiator highly efficient, and allows the use of a very small radiator.

But this small, efficient design is also extremely sensitive to anything that changes its efficiency. Anything that slightly reduces airflow, or which restricts the frontal surface area, will dramatically reduce its cooling ability, causing your ‘Vette to run hot. You can change the thermostat, flush the cooling system, change your “fan-on” settings, replace your waterpump, and tear your hair out, and your ‘Vette will still run hot if the radiator has this one, eensie, weensie little problem….

The radiator in your C4 is shrouded together with the A/C condenser. The Condenser is in the front (clearly visible from the front, underneath side of the car), and the Radiator is in back. Only the back surface of your radiator is visible or accessible – there is no access, even visually, to the front surface of your radiator. The plenum that is created between the condenser and the radiator is a low-velocity air flow area. This area will become the resting place for every single dead leaf, hot dog wrapper, grass, and hairy varmint that your car has ever made contact with. How all this stuff gets in there is one of those mysteries that nobody can explain. After 100,000-or-so miles, the front surface of your radiator will be packed with grass, leaves, oil, dirt, grime, rodent hair and other things that I have yet to be able to identify. You can blow a garden hose through from the back side, but it will not clear out the front surface of your radiator, and you do not know that it has happened (since you cannot see it).

If you want your 100,000-mile (and often less) ‘Vette to run 20 degrees cooler, you have to pull the radiator and clean all this garbage out of the plenum and out of the front surface of the radiator. This should be a mandatory service process for every high-mileage, hot-running C4.


Tools and Equipment Required
As a minimum, you will need the following tools:

1. Long & short flatbladed screwdrivers. One really small one.
2. 10mm socket with long extensions and a 3/8” drive ratchet
3. 14mm 3/8” drive socket
4. 7mm socket with ¼” drive ratchet and extensions
5. 9/16” Flare Nut (“Lion”) wrench
6. Soft, long-haired, nylon brush
7. Antifreeze
8. Dish Soap or K&N Air Filter Cleaner


Procedure
Pulling the radiator on a C4 is remarkably simple. Nothing at all like the C3 boys have to go through. You can do this in about 15 minutes:

· Drain the radiator. I do this simply by pulling the lower radiator hose off at the radiator.
· Pull the upper radiator hose off at the radiator.
· Remove the overflow hose from the radiator.
· Remove your Mass Airflow Sensor (MAF) with its duct. Be careful disconnecting the electrical connector so as not to damage the wires or the connector.
· Remove your air cleaner and the air cleaner plenum from the top of the radiator shroud. The two plastic hand-nuts that hold the plenum to the shroud will often times not come off. This is because the studs on the back side are spinning. You can keep the studs from spinning by jamming a screwdriver between the plenum and the shroud, up against the studs. To fix this, here is a tech tip I received from “LWesthaver” (Wes) on the CorvetteForum: “Lars, I just faced this problem last week. Since I had never seen the underside of my plenum I didn't know how it was attached to the shroud. Finally, after figuring out how to remove the thing, I started looking for a fix. I ended up drilling a 1/8" hole through the studs’ metal tangs and the shroud. Once the studs were re-installed into the shroud’s key-hole opening, I pop-riveted the tangs to the shroud. No more spinning studs! And it even looks like something the factory might have done.” Great tip, Wes. Thanks!
· Remove the 2 10mm screws that attach the A/C receiver/drier bottle to the frame crossover.
· Remove the 2 10mm screws that attach the A/C receiver/drier bottle to the fan shroud (using your long extensions).
· On some years, you may need to remove 2 10mm screws and loosen a 3rd 10mm screw attaching the Power Steering Reservoir and rotate the reservoir out of the way.
· Remove the rest of the 10mm screws attaching the upper fan shroud to the lower fan shroud.
· Remove the 7mm screws running along the front edge of the upper shroud.
· Remove the upper & lower transmission cooling lines using your flare nut wrench. Place a drain pan under the area to catch the few drips that will be lost (you won’t loose much fluid).
· Remove the bolts attaching the fan assembly to the upper shroud.
· Remove the upper shroud.
· Carefully pull the radiator straight up, taking care not the bump the fin surfaces against the cooling fan assembly or anything else.
· Take a look at all the debris inside the plenum and all the crap on the front surface of your radiator. Be aghast.

The first thing you want to do is to scoop all the garbage out of the plenum. Once you’ve scooped it out with your hands, take a garden hose and blow it out good.

Your radiator needs some care. The fins are EXTREMELY fragile – much more so than on the old type of radiators. First, lay your radiator face down on the ground and blast the big chunks out of it with your garden hose. Now, pick the debris out of it that didn’t get blasted out by the hose.

Next, spray the entire face of the radiator down good with K&N Filter Cleaner, or dilute some dish soap into a spray bottle and douse the radiator down good. The front face is most likely covered in grease, grime, and unidentifiable road dirt. Taking EXTREME care, gently brush the front face of the radiator with your soft nylon brush. DO NOT brush from side to side; brush only up and down (you know – like the dentist told you to brush your teeth when you were a kid). If you brush from side to side, even with your soft brush, you will fold the fins right over. Once you have brushed the cleaner or soapy solution into the front face, removing all of the oily, greasy crap and build-up, blast the entire unit off really good with the garden hose again.

Next, sit down on your front steps with a cooler full of beer beside you, place the radiator on your lap, and straighten every one of the bent, folded-over, damaged fins on both sides of the radiator using a very small, flat bladed screwdriver. If you have a lot of damaged fins, this will take some time, but it’s the only way to get your radiator up to its intended level of efficiency.

Once you have cleaned and repaired your radiator in this manner, install it back in the car by reversing the above steps. Fill it up with new antifreeze, check your transmission fluid level, and enjoy a ‘Vette that will often run as much as 20 degrees cooler than it did before.
 

grumpyvette

Administrator
Staff member
Cooling System Operation and Testing


Electric cooling fans attached to the radiator keep the LT1 from overheating when there is little or no air passing through the radiator core (car going very slow or stopped and engine running). It is normal for the temps on the gauge to go up to the middle or past middle of the gauge before the fans kick on. The middle of the gauge is in the range of 210º - 220º. With factory programming, the PCM will command low speed fans (or primary fan) "ON" at 226º and "OFF" at 221º and high speed fans (or secondary fan) "ON" at 235º and "OFF" at 230º. The fans should come on before it gets to any part of the red zone. (see "dual fan configuration" below about primary and secondary fans)
The f-body LT1 uses a 180° thermostat as stock. Crusing temps are generally 10°-20° higher than the thermostat rating.

The PCM gets it's temp readings from a sensor that is in the water pump. If the reading the PCM receives is inaccurate, the fans may not come on at the correct time. The PCM also uses this temperature for lookup in calculation tables. If there is a problem that causes the reading to be always low (cold), the PCM will add extra fuel. This can cause hard starting when warm and an overly rich condition when running.

The gauge gets it's information from a sensor that is in the driver's side head. Inaccurate gauge readings can be from this sensor or it's wiring (the wire burned on a header pipe is common). The temp that the PCM sees can be monitored with a scan tool and compared to the gauge reading. They should be close, but don't expect them to be "perfectly" synchronized.

The fans are programmed to come on when the a/c is turned on. A/c Pressure monitoring sensors feed the PCM info and depending on the situation, the PCM may command the fans off for brief periods. Also, when the car reaches sustained higher speeds, the fans may be commanded off so incoming air can flow through the radiator unimpeded and provide the cooling needed.

Fans will also come on when the SES lamp comes on. The PCM does this when certain (most) DTCs are detected to protect the engine from a situation where it may overheat.


There are two versions of the dual fan configuration:

1993-1994 - Primary and Secondary fans that operate at only one speed. When initially commanded on, only the primary fan (driver side) comes on. It operates alone at full speed. If the temp threshold is met for addtional cooling, the secondary fan (passenger side) also is commanded on. At this point, both fans are running at full speed.
These fans use a two relay architecture that can be seen in the fuse/relay panel that is under the hood.

In late 1994 and into 1995, there was a change to low and high speed fans. When initially commanded on, both fans will come on at a low speed. When the high speed temp threshold is met, they both bump up to high speed. A three relay architecture is used for this fan version (seen in the fuse/relay panel). By adding a third relay, low speed can be achieved by running the power to the fans in series. This way, each fan does not get full voltage and runs at a slower speed. High speed happens when the relays switch to provide full voltage to both fans. Low speed is less noisy and should result in greater fan longevity. High speed is not always needed.


2 Relay System PCM Commanded Fan Operation PCM Wire Color Grounded Fan Operation Relay Operated
#1 #2 #3
Primary@226º Drk Grn @A11 Primary (LH) fan full speed X - n/a
Secondary@235º Drk Blu @A10 Secondary (RH) fan full speed X X n/a
3 Relay System Low Speed@226º Drk Grn @A11 Low Speed (both fans) X - -
High Speed@235º Drk Blu @A10 High Speed (both fans) X X X
For both fans to operate in either system, both relay leads must be grounded. Grounding only the Drk Blu wire will result in only the RH fan operating at high speed.



Here are some fairly simple things to check for various complaints:

~Fans are not operational at any time~


Check fan fuses in the underhood fuse/relay panel
Check fan relays (same location). Aside from getting out any electrical equipment to test the relay, you can swap it with another one (such as the fog lamp relay) and test for function. See if the relay works for the fog lamps and/or the swapped-in relay makes your fans work. Nearly all the relays in the panel are the same, except for maybe the ABS relay.
You can jumper two pins on the DLC that should cause the fans to come on. 1993-1994 cars with the 12 pin DLC can jumper pins A and B. On a 1993, that is the same way that you would retrieve trouble codes from the ecm. The 1994 won't give you any codes, but the fans will engage. 1995-1997 uses pins 5 and 6 on the 16 pin DLC to initiate what is called "field service enable mode". That will cause the fans to come on and operate most sensors for sanity checking. After placing the jumper on the correct pins, turn the key to ON (don't start). If the fans work after jumpering the DLC, your PCM is capable of operating the fans and all fan wiring/relays should be ok.
Deeper problems can be solved through testing and using the wiring schematic.

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~Fans don't come on except when the a/c or SES is on~

~Temp gauge continues to rise with no automatic fan operation~


With a scan tool, check to see what temp the PCM is seeing from the sensor in the water pump. Make sure you are aware of the temps the fans come on (stated in the beginning of this article). If the temp it sees is incorrectly low, it won't know to turn the fans on. Another possibility is that the temp is really ok, but the gauge is reading wrong. That is why you need to use the scan tool to see and compare the readings. Info on testing wiring and sensor can be found here.
If that looks ok, then your PCM may have issues. You could always try resetting the PCM by pulling the PCM BAT fuse for about 30 seconds.


Other cooling issues

~Temps escalate with speed and fans are working~


Check for obstructions/debris in front of the a/c condensor (sometimes even between the condensor and radiator).
Make sure the air dam is on. Cars with low ground effects may need a special air dam to scoop up enough air for cooling.
Check the thermostat for proper operation. It can be tested in a pan of water, heated on a stove. It should begin to open at it's rated temperature and then open fully as it gets warmer.
While on the subject of thermostats, the LT1 reverse flow system uses a special, long thermostat that works together with the passages in the water pump to provide proper coolant routing. If you use an old SBC style thermostat, you run the risk of the system not operating with proper efficiency and it may overheat. Escalating temps can be caused by poor air or coolant flow.


~Generally running hot~


Examine system for any of the items mentioned above.
Check for air in the cooling system via the air bleed screws.
Check or replace the radiator cap (especially if you have heard lots of gurgling and overflow into the remote reservoir. The F-body system uses an 18 psi cap.
Check for any obvious leaks. If needed, rent a pressure tester that will allow you to pressurize the system while it is cool. This will allow you to see if it holds pressure and look for any leaks.


~Low coolant lamp on~


The low coolant sensor is a most common cause of complaint. If it gets dirty, it may cause the lamp to come on when the coolant level is actually ok. Sometimes it fails and no amount of cleaning will fix it. The sensor is only connected to the lamp on the dash. It does not report to the PCM and no DTC's will be set. Because of this, some people choose to simply unplug the sensor to get rid of the annoyance without having to fix it. Unplugging it will make the lamp go out, but you will have to monitor the coolant level yourself. As critical as the coolant is to the LT1, having it working makes sense.

If the light seems to come and go, make sure the level in the remote reservoir is proper. Normal operation of the cooling system often causes coolant from the radiator to overflow into the remote reservoir. As the engine cools down, the radiator creates a vacuum and pulls this coolant back into the radiator. The piping from the neck of the radiator to the reservoir must be air tight for this to occur. Since these cars are getting older, it is not uncommon to get a small leak in the pipe that goes under the battery. Acid wears away at the pipe until it makes a hole. Even a small hole is enough to cause problems. A telltale sign is a small amount of coolant under the right front of the car after it is parked a while. Usually, only taking out the battery will reveal where it is coming from, because it slowly drips on the splash panel underneath and may travel along to another area to drip off.

If the lamp is coming on for no apparent reason (you have verified coolant level is fine-that is, checked the level in a cold radiator and verified you have the proper level in the remote reservoir), you have a few choices:
Clean the sensor and try it again
Replace the sensor
Unplug the sensor (the low coolant lamp will stay off and there will be no monitoring of the coolant level)


Thermostats and cooling

The temp rating of the thermostat is merely at what temp it will begin to open and allow coolant flow. It is purely a mechanical, temperature reactive device and has no external control or monitoring. A frequent reason behind a lower temp thermostat is to be able to make use of more aggressive spark advance without the engine having any spark knock (detonation or pinging). Excessive spark knock is detrimental to the engine. Spark knock is also monitored by the computer and timing advance is pulled (retarded) by the computer. When timing is retarded, performance and power will decline.

There is a fine line between between enough spark advance for high performance and the penalties for too much. The engine temperature plays a role in that the coolant wicks away heat from the combustion chambers in the head. Higher overall engine temperature results in higher overal combustion chamber temperatures. Installing a lower temperature thermostat alone may actually decrease performance because a certain amount of heat is needed to burn the air/fuel mixture efficiently. If you see a decrease in gas mileage with a lower thermostat, alone, this may be the reason. The trick is to lower the temperatures but add enough timing to increase performance over what it was originally.

An often asked question is "Will my engine stay cooler with just a 160° thermostat?". The answer is yes, as long as there is good air flow across the radiator and the cooling system is working efficiently. Note that engine temps will still climb as they did before when you are stopped (as in traffic). However they may not rise as high, since you are starting out at a lower temperature than before. When you are moving again, it will be possible for the temps to lower more than what the 180° thermostat would previously allow. Cruising down the road, your engine should definitely stay cooler than before. Remember that the rated temperature of a thermostat is the temperature that it begins to open. While crusing on a moderate temperature day, an LT1 will generally run 10°-20° warmer than the thermostat temp rating. Make sure you use the correct, long LT1 thermostat (not an SBC thermostat) as described in the troubleshooting section above.

The thermostat only has control of opening temp to allow coolant flow, after that it does nothing but cause a predetermined amount of restriction in the flow. To make the most of the lower temperature thermostat, it should be accompanied by reprogramming of the fans, so that they will come on at a lower temperature. This will help to maintain a lower overall temperature in all driving conditions (especially when stopped in traffic). It is not mandatory that you do this and a 160º can be installed by itself with no other modification.

Something else to consider is that when the engine gets to ~220º (even before the stock fan ON temp of~226º) and you are at MAP loads of 70Kpa or more, the PCM begins to retard the timing. That is one reason why people feel their cars don't run well when they are hot. The GM folks built the retard into the spark tables because when the engine is hotter, there is more chance for spark knock. If you can keep the temperatures from getting up into that range, then you might feel more power when you need it.

Altering the fan ON temps can be done through reprogramming the computer or an aftermarket "fan switch" such as sold by SLP and JET . Manual fan switches can also be wired up to operate the fan relays so that the fans can be operated at any given time the driver wants (like in staging lanes). There are explanations on how to wire the manual switch up on the 'net and there are even a couple of wiring diagrams in the electrical section of my Tech Page. If you look at the fan schematics, you can probably see that there can be several solutions to operating the fans manually (my preference being to control the existing relays).

edited 8/28/2011





Easy Thermostat Changeout



Do this when the engine is cool (like after sitting overnight or for several hours where there is no residual pressure in the system). This way there will be no need to drain any extra coolant from the system.
You will have to remove the intake elbow.
Stuff absorbent rags or towels all around the thermostat housing to catch any coolant when you take the housing loose. Not a lot will come out. Just keep it off your optispark.
Swap the thermostats and put the housing back on. Don't overtighten the bolts, they can easily break (torque to 89 lb. in. - "snug"). No gasket or sealant is needed other than the rubber o-ring that is on the thermostat, itself.
Put everything back together and put whatever amount of coolant you lost back into the remote reservoir. You can also top off the radiator, if you wish. After a few heat and cool cycles, the system will pull back in any coolant that was lost.
Idle the engine and monitor the temp. If the temp quickly goes abnormally high, you may have an air pocket. Open the bleeder screws after the thermostat is open to remove any air. Only a stream of coolant will come out when all air is gone and there will be no spitting or hissing. You can also refer to the refill portrion of the drain and refill procedure, if you want to try to purge air again when the engine is cold.
Close screws and monitor the temp.

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BTW FAULTY GROUNDS, IN MANY CARS AND ESPECIALLY NEWER CORVETTES CAUSE MANY ELECTRICAL ISSUES SO IF YOU HAVE INTERMITTENT ELECTRICAL ISSUES CHECK THEM CAREFULLY
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