Can't Bleed Brakes.

Doodad

Doodad

Active Member
1989 c-4 Corvette. Noticed my brakes weren't grabbing after extended down time on the lift after head rebuild. Raised the car checked right front caliper not moving..bled brakes again no fluid coming from line used vaccum bleed, bleeds fine from other lines. Not the passenger front https://redirect.viglink.com/?format=go&jsonp=vglnk_158497755761412&key=5e9e33f20bf41d5a669cc4838c2690e9&libId=k84mplso01000b28000MAbfzru0rd&loc=https://www.corvetteforum.com/forums/c4-tech-performance/2695311-abs-delete-on-89-convert.html&v=1&opt=true&out=http://forums.corvetteforum.com/c4-tech-performance/2481899-another-removing-abs-thread.html&ref=https://www.google.com/&title=ABS delete on 89 convert. - CorvetteForum - Chevrolet Corvette Forum Discussion&txt=http://forums.corvetteforum.com/c4-t...bs-thread.html

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https://www.appletreeauto.com/METRI...5/?xid_176f4=57b5bc5825059d0a8ff4db877f2643f2

Originally Posted by 86project
I have done this bypass and you only need 2 tee's.
I Will attach a pic of the ABS system, look at the lower right sketch,#15 & 16 go into a tee one line is plugged, you can do that with a bleeder bolt.
#12' 13 & 14 go into a tee.
Look at the top sketch for a description of each brake line.
Click to expand...

48085122d1492551353-another-removing-abs-thread-c4-corvette-abs-pipe-routing.jpg


Brake Hose/Line
Flex Hose
Front 14076178 $29.98
Rear 14091293 $27.50

https://www.corvetteactioncenter.co...and-performance/135632-1987-abs-question.html
 
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ABS on the 1986-91 vettes
how many of you gentlemen have experienced issues with the ABS brake sensors relays or ABS pump behind the drivers seat,>
and if you did what was the cause, symptoms and eventual the cure or parts that needed to be replaced?
I have a 1987 corvette in the garage the owner dropped off, and while I'm sure I will find the issue ,
it always helps to ask for advice as generally theres someone who has already gone through the process and has useful knowledge.
as henry ford once said,
"you don,t need to know how to do everything personally,
you just need to know who to ask among the skilled and experienced people who do know"

I may have to buy a shop manual eventually for that car, but it never hurts to ask questions,
its not as if no one knows the answer after a cars been out in hundreds of thousands of c4 corvette owners hands for decades
bye-passing the ABS may cause more reliability issues than it solves,
yes Im very much aware that the replacement parts are both expensive and at times difficult to obtain.
https://www.vette2vette.com/

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https://www.obd-codes.com/faq/read-gm-2-digit-obd-codes-free.php

http://garage.grumpysperformance.com/index.php?threads/c4-c5-corvette-trouble-codes.2697/#post-70653

to clear ABS/ASR codes do the following:

Same as above but you’re looking for “9.7” on the trip odo

And here are the codes

1994-1995: Diagnostic Trouble Codes
DTC #11: Malfunction Indicator Lamp Circuit.
DTC #13: Bank #1 Heated Oxygen Sensor #1 Circuit:
DTC #14: Engine Coolant Temperature Sensor Circuit Voltage Low.
DTC #15: Engine Coolant Temperature Sensor Circuit Voltage High.
DTC #16: Distributor Ignition System Low Pulse.
DTC #18: Injector Circuit.
DTC #21: Throttle Position Sensor Circuit Voltage High.
DTC #22: Throttle Position Sensor Circuit Voltage Low.
DTC #23: Intake Temperature Sensor Circuit Voltage High.
DTC #24: Vehicle Speed Sensor Circuit.
DTC #25: Intake Air Temperature Sensor Circuit Voltage Low.
DTC #26: Evaporative Emission Canister Purge Solenoid Valve Circuit.
DTC #27: EGR Vacuum Control Signal Solenoid Valve Circuit.
DTC #28: Transmission Range Pressure Switch Assembly Fault.
DTC #29: Secondary Air Injection Pump Circuit.
DTC #32: Exhaust Gas Recalculation.
DTC #33: Manifold Absolute Pressure Sensor Circuit High.
DTC #34: Manifold Absolute Pressure Sensor Circuit Low.
DTC #36: Distributor Ignition System High Pulse.
DTC #37: Brake Switch Stuck On.
DTC #38: Brake Switch Stuck Off.
DTC #41: Ignition Control Circuit Open.
DTC #42: Ignition Control Circuit Shorted.
DTC #43: Knock Sensor Circuit.
DTC #44: Bank 1 LF Heated Oxygen Sensor #1 Circuit Lean.
DTC #45: Bank 1 LF Heated Oxygen Sensor #1 Circuit Rich.
DTC #47: Knock Sensor Circuit Or Module Missing.
DTC #48: Mass Air Flow Sensor Circuit.
DTC #50: System Voltage Low.
DTC #51: EPROM Programming Error.
DTC #52: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #53: System Voltage Low.
DTC #55: Fuel Lean Monitor.
DTC #58: Transmission Fluid Temperature Sensor Circuit Low.
DTC #59: Transmission Fluid Temperature Sensor Circuit High.
DTC #62: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #63: Bank 2 RF Heated Oxygen Sensor #1 Circuit Open.
DTC #64: Bank 2 RF Heated Oxygen Sensor #1 Circuit Lean.
DTC #65: Bank 2 RF Heated Oxygen Sensor #1 Circuit Rich.
DTC #66: A/C Refrigerant Pressure Sensor Circuit Open.
DTC #67: A/C Pressure Sensor Circuit Sensor or A/C Clutch.
DTC #68: A/C Relay Circuit.
DTC #69: A /C Clutch Circuit.
DTC #70: A/C Clutch Relay Driver Circuit.
DTC #72: Vehicle Speed Sensor Loss.
DTC #73: Pressure Control Solenoid Circuit Current Error.
DTC #74: Traction Control System Circuit Low.
DTC #75: Transmission System Voltage Low
DTC #77: Primary Cooling Fan Relay Control Circuit.
DTC #78: Secondary Cooling Fan Relay Control Circuit.
DTC #79: Transmission Fluid Overtemp.
DTC #80: Transmission Component Slipping.
DTC #81: Transmission 2-3 Shift Solenoid Circuit.
DTC #82: Transmission 1-2 Shift Solenoid Circuit.
DTC #83: Torque Converter Solenoid Voltage High.
DTC #84: 3-2 Control Solenoid Circuit.(Auto Only).
DTC #84: 2nd And 3rd Gear Blockout Relay Control Circuit.
DTC #85: Transmission TCC Stock On.
DTC #90: Transmission TCC Solenoid Circuit.
DTC #91: One To Four Upshift Lamp(Manual Only).
DTC #97: VSS Output Circuit.
DTC #98: Tachometer Output Signal Voltage Wrong.



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abs relay
https://www.vette2vette.com/products?search_api_views_fulltext=abs pump&f[0]=field_years:1987&f[1]=field_category:12

https://www.rockauto.com/en/catalog...1220,electrical-switch+&+relay,abs+relay,3008
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Originally Posted by jv9999
I hesitate to mention this, but I had the same problem and fixed mine. If you're the adventurous type, consider this: There are three solenoids in the pump, one for each front wheel and one for both back ones. The one for my LF was stuck shut, probably from moisture in the fluid.
I figured out which line was the LF and which solenoid controlled it. If you remove the relays and the plastic cover over them you can access the connections for each solenoid. I sprayed penetrating oil in the appropriate line opening and kept cycling the solenoid with a battery charger. Eventually it opened up. I then flushed it with brake fluid and reinstalled it. It's been a year now.
Use this information at your own risk, or just buy a replacement. Either way, keep the fluid fresh.
Click to expand...

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1986 ABS Light On
Just a quick question to all those that have had experience with the Bosch ABS system, since it could save me some time and $$$; when I turn the key to the on position, I hear the relay one of the relays click about 3 times and the ABS light flashes in unison as well, then the light goes out; it will stay out until I begin to drive, and then it will stay on; I am familiar with the fact that the system is supposed perform a self-test at about 4 miles per hour, which unfortunately, the system is not doing now; before I pick up one of the Kent-Moore J35890 ABS testers on line, which I can get pretty cheap, are there any other easy checks to perform? I have the FSM, however it doesn't say you can do much other than check the "BRAKE" and "GAUGE" fuses, and make sure all the wheel speed sensors are seated properly; any suggestions to those who have gone through some testing? I'm guessing it's probably not the relays, since I can hear one clicking; hopefully it's just one of the wheel sensors, but will need the tool so I don't just start replacing unnecessary parts; actually, now that I'm mentioning it, does anyone have the AC Delco parts #'s for both the pump motor and solenoid relays that sit on top of the modulator valve? If they are fairly cheap, I may start with those 2, since even though I can hear one of them clicking, not sure if the other is working as well.......


Regards, Chris
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You might try to get up to 60 or 70 and jump into the brakes hard enough to get them to activate. Believe me it takes a lot of effort to get the abs to work but the shaking and pulsing of all the sensors may brake lose a stuck sensor. Bring the car to a complete stop and then do it again. Be safe and pick a good clean road that you can tell there is not other cars near you.
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I'm most familiar with the system on my '89, but assume it's basically the same. There is a decent amount of diagnostic stuff in my FSM not pertaining to the factory ABS testing tool. Runs through the typical troubleshooting of specific components in the system, lists sensor specs to test against and wire colors for each individual sensor, describes the "sequence of operation" for the system, etc. Maybe your earlier manual doesn't have that same info. Also, I believe someone posted a link, perhaps last summer - it had some tips for doing ABS troubleshooting without the factory diagnostic tool, ran through a process for checking the relays, etc. Maybe that might show up in a search or perhaps someone else remembers it. I probably printed copies, if I can find them. Anyway, I was able to diagnose my own system using only a DMM using the information in the FSM and the extra information I mentioned. It took me a while to run through all the tests listed, as there are circuits in a number of places that need to be checked and of course none of it is easy to get at. Ultimately everything tested out "ok" and my actual control module was the culprit. To your own situation, am I understanding that the lamp goes out once the vehicle starts and stays out until you drive? Once you start to move, the control module looks for signals from the wheel sensors. If it doesn't see those signals, the light comes back on. So, a wheel sensor would be my first guess. Depending on what you're most comfortable doing first, both mechanical inspection and electrical testing would be appropriate to see if the sensors are at least in place and intact electrically.
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yeah READ THE LINKED INFO IT HELPS
https://www.corvetteactioncenter.com/tech/c4/abs/index.html#.UT4dfI6ubd4

https://www.corvetteactioncenter.com/tech/c4/abs/abs_page2.html

https://www.corvetteactioncenter.com/tech/c4/abs/abs_page3.html

https://www.corvetteforum.com/forum...ible-substitute-for-kent-moore-j-35890-a.html

https://corvettesalvage.com/1986-to-1991-corvette-abs-brake-pump-fix/


https://www.ebay.com/p/1611874538?i...MIptyYs6Ox6AIViODICh19aAPYEAQYASABEgKNQ_D_BwE
 
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But I believe that a few other manufacturers from the 80s were using the same abs system including vw,caddilac, and BMW. My brake line tees just arrived there will be two open orifaces that need to be plugged, I forgot to order them.
 
Grumpy you said above that removing theABS may be worse than fixing the pump, can you elaborate? My intention is to just get the car on the road to get me going until I can look into the 350-500$ repair or new pump, I already understand the breaking/anti skid properties of the ABS
 
http://www.superchevy.com/how-to/19239
Here's another good article on the early c-4 brakes.
As I understand it. These are valves controlled by high speed solenoids. Although I've read about the failure rate of these pumps from brake fluid corrosion, what I haven't heard yet here is the solders on the control board, like all these 80s circuit boards checking for dull or cracked solders can remedy many a problem. I have an article here I'm looking for on the control board rebuild. Interesting read. I'll post when I find it.
 
I was under the impression that these valves remain open (actually centered) until the abs software engages the solenoid. What I mean is the lines are open until panic brake (bias not affected). I thought the c4 had a self centering proportion valve on the MC. Then a bias valve up front near the Radiator where the brake lines meet.
 
What I'm saying is wouldn't the bypass give the same bias as the abs system only until loss of traction braking
 
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