[Scorpiooooooh]

This problem has been resolved. Thank you to all who offered suggestions.

Hi folks,

Need some assistance diagnosing a problem with ABS/TCS on my 94 Concourse. A little background info first. After I replaced my break pads all around and the front and rear right side calipers, the car ran fine. I did notice a slight rubbing noise from the right front rotor but figured I just had to wait for the pad to seat itself. About a week later my right front rotor got smoking hot at highway speed, so hot it was cooking off the grease anywhere near the hub and control arm. Scared the crap out of me, if I had gone any further it probably would have reached flash point. So I limp the car back home and park it. Take a look again to see if I botched any part of the job. Everything seemed good but since the rotor got so hot it warped. I replaced the rotor and put everything back together again. I get ABS and TCS warning now even though everything mechanical seems to be working well. No more rubbing noises etc..

So my question is this; Is it possible I cooked the sensors in the wheel hub assembly? My mechanic ( yeah, I buckled and sent it off) said the ABS module went bad. After reading a couple dozen posts here it seems many ABS problems originate from the right front hub. So I have to make a decision, replace the hub or replace the whole ABS system. I know the standard procedure is to provide the codes with descriptions, but I don't have the car with me to do that. Did a fault in the ABS module cause the rotor to hang or did I cook the hub and now the sensor data is unreliable? Any help much appreciated.

 

[rodnok01]

Sounds like the caliper wasn't in far enough and or sticking.
Yes you very well could have cooked the speed sensor in the hub or even the wiring. First thing I would check would be the codes... second would be wiring to that wheel.

 

[mc_marto]

Like rodnok said, check the codes, and then the wiring to the sensor. When I bought my car it had the ABS light on, and what I discovered a year later was the ground sleeves on both front speed sensor wiring were cut off. A couple of minutes later I soldered bridges to repair the grounds, then key on - the ABS light disappeared.

So, check the wires.

 

[Scorpiooooooh]

Since the car is nearly 20 years old, I think what I'm going to do is go ahead and replace the front hub assemblies. I plan on keeping this car for a very long time and they will eventually need to be replaced, so I'll chalk up the expense to PM. After reading a bunch of posts about ABS/TCS problems, it would appear that the r/f hub is the most likely suspect anyway. For some reason that particular hub seems to be the cause of many ABS/TCS problems. Also, while possible, it is very unlikely that the problem is with the ABS system itself. From what I've read the ABS systems are extremely reliable. If you (or anyone else reading this) agree or disagree, then please let me know.

 

[MoistCabbage]

You need to pull your codes. A faulty wheel speed sensor will throw a code. If there isn't a code for it, and there's no play, there's no need to replace it. Hubs are either good or bad, there is no "starting to wear" stage at which to perform preventative maintenance.

If there was a problem with ABS or TCS, a code would have been thrown, and the system would have been disabled. If the system was functioning properly, it would not have operated long enough to allow anything to overheat. The system disables itself when it estimates that ABS or TCS has been applying the brakes enough to cause overheating.

The cause for the rubbing was mechanical. And FWIW, rotors don't "warp". Excess pad material can build up on rotors if you come to a complete stop with HOT brakes, causing vibrations and pedal pulsations.

 

[donwon]

The flexable lines could be deterated and not letting the fluid bleed off when you take your foot off the brake pedal.
I have had this happen before. Could have been the start of your problem.

 

[carnut]

I agree with donwon. Restricted hoses to calipers are overlooked and many calipers are replaced in error! The hoses flake off rubber internally and the fluid cannt return to the master cylinder once the pedal is released. The best way to verify its a hose is to open a bleeder screw on the bound up caliper. If the caliper releases, its the hose. If the caliper remains bound up, its the caliper or guide pins. And why did you replace the right side BRAKE (break) calipers in the 1st place?

 

[Scorpiooooooh]

The caliper went bad, the seals were shot because the rubber boot around the piston deteriorated. As for the hoses, when I bled the lines everything was fine, no blockage, line gunk or restricted flow. The problem cannot be the lines though, I had them all replaced because they were corroded and leaking. I ordered a set of hub assemblies for the front end. I'm going with my first instinct that the sensors got cooked when the rotor overheated. We'll see how that works out.

 

[MoistCabbage]

Again' pull the codes. If the sensors are bad, they'll tell you.

 

[mc_marto]

Again' pull the codes. If the sensors are bad, they'll tell you.

I'm not sure about that. When my grounds to the front sensors were open there was no code triggered. I believe the ABS system has to be diagnosed separately. Except, if '94 is different than my '91.

 

[Scorpiooooooh]

Problem solved, woo hoo! ! ! So it turns out that the sensors on the hub got cooked when the rotor overheated. The new set of Moog hubs cost $147- and labor was 125, so not too bad.