TR6

I've searched through previous posts on this, but didn't find anything that seemed to be exactly my situation. I started off this morning from home to drive the RSA (C2) to work and got only a few minutes down the road when the ABS light and "!" light along with the audible alarm came on steady. I exited and turned back home. The lights stayed on the whole way until I pulled back into the garage and turned it off. I was running late already, so I left it and took my truck to work.

Background: Several weeks ago, I did a DE track weekend during which I experienced some brake fade/ soft pedal in the last session of the last day from what I assume were overheated brakes. The day before the DE, I had the brake fluid flushed with ATE super blue, so the fluid was fresh. On the way home from the DE that evening, the speedo needle started jumping a bit. But no ABS light came on.

I didn't drive the car for a week until the following weekend (about 2 weeks ago) I took it out to the track for a session of moderate laps (wasn't pushing it too hard) where I noticed that the pedal periodically went just a bit soft on me and even a little uneven resistance in the action of the brake pedal. I firgured that I probably boiled the fluid and got a little air and/or moisture in the system at the previous week's DE and that I needed to bleed it. I took the car home and put it back in the garage as I was leaving for vacation the next morning. Since then, I haven't had time to have the brakes re-bled or flushed. Then this morning, I drove it again and as you saw in the first paragraph, the ABS light has come on. I am hoping to bleed the brakes this weekend.

Would the overheating or boiling of the brake fluid at the DE 3 weeks ago cause the eventual lighting of the ABS warning? I've never had it come on previously. If so, will bleeding or flushing the hydraulics solve the problem? I don't have Adrian's book with me at work (yes, I do own it), but in my rennlist search, I read several threads that talked about checking the voltage at the sensors. But I can't help but think that the overheating of the brake system at the DE may have ultimately triggered this. Anyone else have their ABS light/warning come on as a result of overheating on a track day?

Nader Fotouhi

Have you tried cleaning the ABS sensor? I do not know how it is attached on a 64, for on a 44 you use an allen wrench to remove and clean. I had to do this a couple of weeks ago at the track.

I do not know whether the ABS light is related to brake issues you describe, but I venture to say if you have brake (which sounds like you do if you drove it home), then they are not. If the ABS light goes out after cleaning the sensor, then flush the brake the system before next track day.

C24FUN

I had the same problem. It turned out to be a loose nut on the positive battery terminal where a 12v feed specifically for the ABS is terminated.

Jim G.

TR6

Thanks for the tip. I'll check it out. I haven't had a chance to diagnose the problem yet or bleed the brakes, but I did drive the car this morning and the ABS light is no longer on. Not sure what to make of that.

Gregg-K

I've had this same ABS warning light problem intermittently on my C2, and have not yet been able to diagnose the root cause. Near as I can tell it is a loose connection because it first started doing it only during hard right turns ... and then it began doing it on hard bumps.

Interestingly I had an almost identical problem with my MK4 Jetta, and that turned out to be a bad connection to the ABS fuse ... but I didn't figure out the cause until after I replaced the fuse panel. Tried inspecting and cleaning all the electrical connections and relays in the C2 with no improvement, but it's never bothered me much because ABS is a pretty silly feature for these cars in my opinion.

I've begun to suspect an intermittent break in a wire leading to one of the wheel sensors, but I decided to wait for a "hard" failure. Just before I put it away for the winter, the problem became much more consistent, so this spring I'll be digging into it more seriously.

.. Gregg

Smokin

IIRC there is a relay under the hood that you should check. The last time I had someone service my A/C (I do it myself now) the guy switched a few relays under the hood. When I started the car the ABS light lit up. I was puzzled but knew the guy did something wrong. I retraced all of his steps and took out the manual. I noticed he took out the ABS relay and put it back in the wrong spot. I think the ABS relay is the same for the A/C (Or something else under there, I can't remember.) It's quick & easy to check to see if that is what the problem is.

Check your relay...

Gregg-K

Good suggestion, but I not only checked the relays and their sockets, but I also dismantled each relay to check & clean their contact faces, as well as to touch up the soldering on the small circuit boards inside (which some of them have).

My car's entire electrical system is exceptionally clean, so that's why I'm suspecting a loose connection or an intermittent break to one of the ABS wheel sensors.

. Gregg

TR6

I may have found the problem. Time will tell. I finally had time to look at the car and I had planned to bleed the brakes since I suspected they might need it (symptoms were sporadically spongy brake pedal and the ABS acting up). I quickly found that the axle spindle on the front left was loose and wobbling! The nut had backed off partially! I could wobble the whole rotor/hub assembly. (A few weeks ago, I had the front wheel bearings replaced) It is now re-tightened and the brakes feel fine. We'll see if the ABS light comes on again, but so far it hasn't. Which begs the question: If the axle spindle and hub were loose and wobbly, could that trigger the ABS warning?

ps. The mechanic checked the other side too and it was still tight, but he put locktite on it and re-torqued it to be sure.

Gregg-K

It's a bit of a stretch, but a wobbly hub caused by a loose wheel bearing would cause the gap between the sensor and the ABS disk to vary. That would would cause the output of the ABS wheel sensor to produce a strange signal, likely outside of normal limits.

Plausible that may be the problem, and like you said, time will tell!

.. Gregg