overheating?

grumpyvette

Administrator
Staff member
" grumpy?
Ive got an Oil pressure and overheating problem
Ive had both these problems for a while now in my 87 corvette and it seems like what ever I do it does not go away. The overheating problem started when the ground for the outer fan went bad I replaced it but the problem persist and after driving the car for 30 min or more the car will reach 260 and the reservoir will start to boil. When the car reaches around 200 the oil pressure gauge starts to read 0 when I'm idle and I know thats not normal because the normal operating temperature is 230 for these cars. Ive replaced the water pump and thermostat but still no luck. I need help! "

Corvette – Water Pumps
The "Corvette short" water pump which you refer to applies only to small blocks and not big blocks. ALL 65-74 Corvette big blocks use the same, BASIC water pump casting (although 4 different castings were used). All 65-70 big blocks use a bearing/shaft assembly with a 3/4" diameter shaft, but a PILOT (the end of the shaft which centers the pulleys and fan clutch) turned down to 5/8". 1971-74 big blocks use a full 3/4" pilot.

For Corvette small blocks, ALL 55-70 Corvettes use a "short" water pump with a 5/8" shaft. This same style water pump was also used on all 55-68 small blocks used in all other Chevrolet passenger cars with small blocks. In 1969, most Chevrolet small blocks and big blocks, EXCEPT CORVETTE, went to the "long" water pump which still used a 5/8" shaft. Block to hub face is 5-5/8 (5.625)

In 1971, virtually ALL of the small block water pumps changed. All, EXCEPT the CORVETTE, continued to be "long leg" style but with 3/4" shaft and 5/8" pilot. Corvette continued to use a "short leg" water pump, but it was a DIFFERENT short leg water pump than used for 55-70 Corvettes. This water pump, often referred to as the "Corvette short" water pump, was set up to accommodate the large bearing and shaft assembly which used a 3/4" shaft. For 71-82 Corvette pumps, the shaft PILOT was the full 3/4". The full 3/4" pilot small block water pumps are unique to Corvettes and some medium/heavy duty trucks which also used the "Corvette short" water pump. I might also add that 71-74 Corvette big blocks ALSO used the 3/4" pilot shaft and they were the only big block water pumps which did so.

Due to its design, the "Corvette short" water pump has a slightly greater block mounting surface-to-face of hub flange dimension. Block to hub face is 5-13/16 (5.900). Combined with the fact that the 71+ pump has the full 3/4" pilot, it is applicable to only 71+ model Corvettes (and the trucks mentioned). The "Corvette short" water pump is NOT applicable to 55-70 Corvettes unless the entire pulley system, fan clutch and fan are changed to the 71+ configuration.

I might also add here, for clarification, by water pump SHAFT diameter, I am talking about the portion of the shaft that goes THROUGH THE BEARING. All Corvette water pumps use a 5/8" impeller shaft end. For 65-70 small block Corvettes, this means that the shaft is 5/8" all the way from end-to-end. For 71+ Corvette small blocks, the impeller end of the shaft is turned down to 5/8".

There were several GM castings used for the 55-70 Corvette and 55-68 ALL small block "short" water pumps. However, for the 71-82 "Corvette short" water pump, there were only 2 castings ever used. 1971-early 1972 used GM #3991399. Later 1972 to 1982 used GM #330813. These are the only 2 castings which GM EVER used for the "Corvette short" water pump. The 3991399 has no drilled and tapped boss on the top for external bypass. The 330813 does have a large upper boss and 3/4" NPT fitting for external bypass. The external bypass provision was plugged with a square head pipe plug for all 72-82 Corvette applications. The fact that this boss and tapping was added to the pump was only for the truck applications that also used it.

Chevy Water Pump Specifications Summary:
Short-Style Pump for most 1955-72 cars & trucks (5/8" pilot shaft)

• Fits all 1955-68 S/B Chevy passenger cars, 1969-70 350 c.i.d. Corvettes and 1955-72 light duty trucks. Has 3/4" ball/ball bearing.
• Dimension from block surface to hub: 5-5/8". Inlet diameter: 1.80".

Long-Style Pump for 1969-87 V8, 90° V6 & 1973-86 truck (5/8" pilot shaft)
• Fits all 1969-87 S/B Chevy or 90° V6 passenger cars and 1973-86 light duty trucks. Does not fit Corvettes (use #8810 or #8812)
or late-model vehicles with serpentine accessory drive belts (use #8881). Has heavy-duty 3/4" ball/roller bearing.
• Dimension from block surface to hub: 6-15/16". Inlet diameter: 1.80".

Short-Style Pump for 1971-82 Corvettes 3/4" pilot shaft)
• Fits all 1971-82 S/B Corvettes. Comes with heavy-duty 3/4" ball/roller bearing.
• Dimension from block surface to hub: 5-13/16". Inlet diameter: 1.80".

350-waterpump.jpg


id-waterpumpchevy.gif

viewtopic.php?f=32&t=3954&p=10553#p10553

Fan86-89.jpg

86-89 fan wiring
viewtopic.php?f=32&t=3954&p=10553#p10553

just some random thoughts

(1) there are both clock wise and counter clock wire rotation water pumps, if you installed the wrong design that would cause your problem

(2) whats your coolant and oil levels?

(3)do both fans come on when you turn on the air conditioner?

(4) have you checked the sensors

(5)have you checked for a leaking head gasket


(6) what do the spark plugs look like, can you post clear pictures of all 8 with the cylinder labeled?

(7) if your fairly close to being local, (Im in western palm beach) if you want to drive it up here Ill help you isolate and cure the problem

(8) have you tried replacing the OLD T-STAT with a NEW 180F T-STAT with a few 3/32" holes drilled in the flange?

(9) have you cleaned all the trash out of the radiator fins with the car up on a lift?


(10)the links below should help
the t-stat controls COOLANT temps,
which are generally 15F-25F lower than peak oil temps,
obviously the coolant temps vary as the t-stat opens allowing flow ,
and closes as temps drop off.
your oil temp may read only 10F hotter than the coolant temps,
but its a fact that oil temps vary a great deal during the trip from sump,
oil pump, valve train,and bearings and back to the oil pan sump.
get out a high quality infrared temp gun, and scan the valve springs after 10 minutes of engine run time,
youll notice the oil temp on the rockers is significantly cooler than that flowing over the valve springs
this is the most consistently accurate I.R temp gun I've used for testing
42545.jpg

http://www.testequipmentdepot.com/e...1100200223789&utm_content=All Extech Products
INFRARED TEMP GUN

Wide temperature range from -58 to 1832°F (-50 to 1000°C)
any time that your dealing with a potential temperature issue or a trouble issue where
, knowing the exact temperature vs what a gauge might say,
\it helps to have a handy and accurate infrared temp gun handy,
to locate and confirm heat, levels.
http://forum.grumpysperformance.com/viewtopic.php?f=32&t=3954

http://forum.grumpysperformance.com/viewtopic.php?f=57&t=149

http://garage.grumpysperformance.com/index.php?threads/cooling-off-that-c4-corvette.3954/#post-10553
 
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