Well my abs light has been on ever since i bought the car, brakes work great but the anti lock doesnt. Anyway, i was driving around today and went over to a friend of mine (has a mint 928 s4 red) and the light came off. I thought maby it fixed it self, i went out driving a little and it came back on. This is the first time i went off like that, any one have any ideas why it did that?

 

Are the ABS sensors clean and working? Are the little "gear" like things on the spindles clean? If not then clean them off and see if that helps. My other reaction is that the ABS brain could be shot.

 

where is the abs sensors? are they easy to reach without removing anything?

 

Ok, i took the car out for a drive yesterday and i was about to come to a stop and i heard a little "servo mechanic" sound coming from the glove box area for about 1 sec and the ABS light came of. I tried it by braking hard on some gravel and the abs kicked in. I have had the car for about 3 months and the light has been on ever since i got it. Anyone know why it just came of like that? It came of about 1 month ago but came back on after about 1 mile of driving. Im thinking the sensors are dirty and i dont know where they are located. Anyone have any pics or the sensors? Any help would be great!

 

Well, drove the car for 100 miles yesterday and the light came back on. Guess its just the sensors behind the wheels.

 

My '89 S2 does a very similar thing, and I still need to clean the 'gears' on the spindles. The servo sound is the brain doing a 'self test' (I think...). There's also some ground wires on the struts that you can check pretty easily, one of mine was loose but nothing changed after I tightened it.
My car must be in an earlier state of this than yours, it works for a while, but then shuts off (often during an auto-x run), but always works on start up. As I understand it, if the sensors and gears are clean, it's then very likely that the brain is bad.
I've heard that some shops have special abs diagnostic tools, one mechanic I know (who borrowed one once) found some wires that a rat had chewed on.

 

ok, how do i find the location on the gears/spindles?

 

send me an email, jimchristensen at yahoo.com I'll ask my mechanic friend and email you back... we'll get through this!

 

well i think you guys are sick of hearing my ABS stories but im going to ask for some advice. Ever since in bought the car (about 3 months ago) the ____!____ and the abs light has been on. If i hit the brakes hard they just lock. The previous owner drove the car for about 500 miles the last year he owned it. He never drove it during rain or snow so i dont think the abs brakes ever have engaged but maybe once or twice during the 16 years that he had it. Well i have put about 1000 miles on it the past 3 months. There was some snow here but it melted so i took it out and was driving and the light came of again. I found a little patch of unmelted snow on a empty parking lot and drove over it and hit the brakes and the abs worked great. Backed up and did it again and again about 5 times and they worked great. Also, before the light came of i heard that servo sound again from the glove box area. My question is, is it possible that the abs brain just has a bunch of dust on it from not ever been used? Or is it getting ready to just be on permanently again because it has been turning of and on because i have been driving it more then the previous owner? Any ideas would be great.

 

Even though, I don’t have a direct answer to your question, here is some information. When I bought my car, the ABS light was off, but the ___!___ on with no other warning lights on. In addition, my abs would set itself off under normal braking. I got annoyed and pulled the ABS relay out. That light the ABS light at the top of the temp/fuel gauge section in addition to the ___!___ light. When I shook the relay, something rattled inside and I assumed it was the problem! I took it apart (having fixed other relays but soldering traces, wire, etc.) in hope of seeing what is wrong. However, this relay is a special, high reliability one – I destroyed it taking it apart just to find out it was ok – a little insulating film to separate PCB with the aluminum case is what was rattling. Since then, I replaced wheel bearings up front and CV joints in the back. In both cases I cleaned the ABS sensors. But since I am to cheap to spring $100 for ABS relay, I don’t know if that fixed the problem.

Moral of the story – even though something rattling inside at $100 dollar relay, it may not necessarily be broken!

As far as location of the sensors, you have to pull the wheels off. In the front, they are on the top of the steering knuckle just behind the brake rotors. Same in the back. They are mounted by one allen screw and just slide inside the knuckle. They are easily cleaned. The toothed wheels are harder to clean and they are an integral part of the spindle. Not sure how to best clean them w/o pulling lots of stuff off.

NOTE: being it your brake system – I don’t assume any responsibility for the above advice. It is all up to you! Being it a brake system, I would recommend taking it to a qualified repair shop!

Not sure how helpful it was,

Thanks