OldGray320i
OldGray320i Dork
11/4/17 12:44 p.m.

Ok, so the old e30 (daughter's car now, and selling it...) has the abs "function" or "apply" at normal braking, but only within the first couple applications of the brake pedal.  After that the car brakes normally, and the ABS light comes on.

Is this the old "abs module fix" found on R3vlimited, or something else?

Streetwiseguy
Streetwiseguy UltimaDork
11/4/17 2:07 p.m.

It sure is common on euro abs from the 90's. I have found they usually will not set the light until the pump and solenoids actuate and rattle the module.

Tyler H
Tyler H GRM+ Memberand UltraDork
11/4/17 5:35 p.m.

My E28 did that too. 

Check the "tone rings" at the hubs for corrosion and missing teeth.   Check the ABS sensors for rust scale and magnetized crust....but they'll probably disintegrate when you do, so just replace?

It's probably a bad sensor or broken ring.

OldGray320i
OldGray320i Dork
11/4/17 6:34 p.m.

 Yeah, a little more searching has me thinking sensor issues. 

Been so long since I've read up on e30tech, r3vlimited, etc...

I'll pull the sensors and clean;  I think one can check continuity and or voltage on them, that'll be next. 

ddavidv
ddavidv PowerDork
11/5/17 8:14 a.m.

ABS problems on the two Spec racers I've fixed have been the following:

Dead sensors (there is a procedure of disconnecting one at a time to find the culprit)

ABS brain (pretty unusual...and the car also had a bad sensor. That was fun figuring out)

Damaged wiring harness. This one really had me going for awhile. What happened was the wiring harness that runs across the front of the radiator/front panel had come loose (old brittle plastic clips). Harness fell into the a/c fan and got chewed up. Spliced it back together and all was fine.

Those systems are pretty simple. It is most always a sensor issue though.

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