When starting the car cold, backing out of my driveway, I hear and feel in the brake pedal a little thump and the ABS light comes on. The only other sound is what I can only describe as a spring sound... like the spring door stoppers behind the doors at my parents home that I grew up in and would pull to the side and release just to hear it... Just not as loud. This last for 2 seconds and all clears up drives and brakes fine. I had the brakes checked when I bought it, front brakes are new... anyone else experienced this?

 

Are you using the parking brake, sounds like it might not be fully releasing and needs lubrication.

 

Never used it. But, I will check it out!

 

Otherwise I'd take another look at the brakes. Usually when they check out a car you're buying they only do a visual check of the brakes for rotor and pad thickness. This could also be an issue with a caliber that is sticking.

 

This is a head scratcher, mainly because some of the things I'm hearing is not likely to happen if I understand the situation correctly.

First off I'd break the situation down in to steps: 1) start the car but hold there 2) put the car into reverse but hold 3) back out of the garage 4) stop backing out and depress the brake pedal.

Where does the sound and light appear?

There is a self test when the car starts but mine is done in a second or two from the time the key is turned on. I don't think the abs system is even used till the car is over a set speed so it's unlikely it's kicking in if it's working as it should.

 

I don't know that what you're experiencing isn't NORMAL - you don't mention year but the system does do a system check. The ABS light should light under certain conditions and for most early years should be lit during crank. Using your "year" maybe search expected ABS system check on start-up. You've been here since Sept '17 so I guess this car is "new to you" as well maybe at about the same time.

 

What you described is normal. When the ABS system turns on you will feel a pulsation in the break pedal. When the ABS Control Module finishes its checking routine the ABS light will turn off and normal driving continues.

I have a different problem with my ’87 convertible. ABS light comes on at startup and doesn’t go out. I bought this car new in ’87 and it is in excellent condition. 56 k on the dash, well maintained, garage kept and never abused. All of a sudden one day the ABS light stays on.

The service manual explains how the ABS system functions and also shows the wiring. At startup 12V powers the coil in the Module Relay. When the relay contacts close it send 12V to the ABS Control Module. The ABS Control Module does a self check and tests voltage at input and output terminals. If everything is ok the ABS indicator light loses its ground and the light (on the dash tell tail) goes off. There is another relay that does have an effect on the ABS light that is part of the Modulator Valve. I did not check its function.

My first thought is that the Module Relay (BOSCH 1636973) is not functioning. If no voltage is sent to the Control Module, it senses a malfunction and the light stays lit.

I removed the relay and applied 12V to the coil terminals. With a continuity tester across the contact terminals, I got an open reading.

I am trying to find a replacement relay (not available - no longer in production). If I find something I will add to this thread.
.

 

NM

You're not out of luck just because you can't find a abs relay from GM.
The same parts were used in a lot of different vehicles in that era:

Module Relay 0332002171: BMW E30 ABS Anti Lock Brake Pump Relay 318is 318ic 325i 325is 325ic 325ix
Mercedes W126 W123 W107 W124 W201 relay 0332002171
0 332 002 171 | PORSCHE / AUDI / VW OEM ABS PUMP RELAY
Solenoid Relay 0332205003; BMW E30 Mercedes Corvette ABS Pump Breaking System Relay Bosch 0332205003
NEW Bosch Relay (ABS) 0332205003 BMW 34511154919
ABS SYSTEM RELAIS VOLVO 740 - 760 - 780 - 940 - 960 / BOSCH 0332205003

Possible alternative for 0332512006: 0332512007. That one has a skirt that would have to be trimmed, but first look appears it may be the same relay in a different housing.

Here I think is a new copy of that sensor cable from Autozone that might work on our C4's but have not seen one in person:
Duralast Brake Sensor - ABS
Image of Duralast Brake Sensor - ABS : Part number SU11958
Part Number: SU11958
Alternate Part Number: SU11958

Mine started having the ABS light come on solid and stayed on. When I bought the car 4 yrs ago it did it on occasion and if you stopped and started the car at times it corrected itself. Eventually it was always on solid once the ignition key was turned on till the car was shut off.
I started looking and checking and figured out the above info. I bought a couple of relays off Ebay, one for a Mercedes and one for a Porsche (IIRc the total for both was under $40). Both exactly matched the ones in the Vette in make, model, size and color. Mine was the silver one on top of the abs pump that was causing the problem, changed that one and everything was good to go again.

Hope that helps someone out.

 

Okay hc, I'll check this out.

Thanks so much for the info.

Regards,

Bill C.

 

Oh ****!!!! Dont let aklim see this post.... he'll have your car flat bedded off to the junkyard....

You can pull all 4 sensors and clean the magnetic pick up end off with some brakleen and rag. Be careful with the electrical connections... they can be brittle. The light on my 86 was on solid and cleaning the pick ups solved the issue.

 

That is true. I'd already had mine out and cleaned and didn't make a difference. What got me tracking down the relays was one day I had the compartment over the abs open and tapped the relays in there a couple of times and the next time the abs light was out. Couple of restarts and it was back to being on solid, which is why I pursued the relays as the cause of my issue.

I've had more than one thing on this car that tapping a relay etc with a screwdriver handle or plastic headed hammer will free something up. If they're openable you can try filing the contacts but more times than it's simpler to just find a replacement.

 

Great work hcbph . Now can you come up with some alternate sources of Bosch ABS wheel sensors?

 

Take a look at this I noted above:
Here I think is a new copy of that sensor cable from Autozone that might work on our C4's but have not seen one in person:
Duralast Brake Sensor - ABS
Image of Duralast Brake Sensor - ABS : Part number SU11958
Part Number: SU11958
Alternate Part Number: SU11958

I'm not sure if they'll work or not but there's enough similarity they just might. They're double holed so just 'might' bolt up, then again maybe they won't. I don't need them so didn't go into it any further than finding them in the first place.
If you do check them out, let us know what you find.

Paul