Weird brake problem: brakes work too well!?

[Headache]

My wife owns a '91 XJ with the infamous Bendix-9 ABS/brake system.
(BTW: I know that it is a POS system and that I should get it replaced).

When my wife started the car this afternoon, she felt that brake pedal was rock hard an hardly giving in under pressure. When she drove away, she had the feeling that this was not going as smoothly as usual, but nothing strange happened until she had to brake. When she applied only a little pressure to the brake pedal, the car came to an immediate halt, as if the brakes were working too well. I do not know if the brakes in fact locked up.

She has driven the car for several kilometers and approx 30 min afterwards, and the problem did not re-occur.

Any ideas what this might be?

Many thanks (again) in advance,
André

 

[beav350]

I'm probably off on this, but, I believe the rear drums are designed to "self-adjust" while reversing, & I've had mine (over adjust?) before & had to work 'em a bit to get them to relax (wear down just a bit). If she didn't have to reverse her way out of your driveway then my theory is shot.

 

[DDCxj]

If it only happened that one time then it was probably some moisture in the rear drums. And it doesnt take very much moisture to do this. A nice spring morning with a little dew on the grass is sometimes all it takes but after drying them off (holding the brake down for a short time while driving) or a couple miles driving around they are fine. A lot of the GM trucks do this too. If its something that keeps happening you might wanna take your drums off and make sure the wheel cylinders aren't leaking. Also leaky axle seals can cause this too but it would be an ongoing problem, not a one time deal.

As far as the self adjusting system goes, its usually the opposite with that. The rear brakes tend to do nothing cause its such a crappy design.

Dean

 

[Headache]

Thanks for your replies. I think that the 'self adjusting' is not the case, as my wife stated that she did not drive in reverse.

I will see how it develops and subject the drums to a closer inspection if the problem re-occurs.

Many thanks,
Andre

 

[rock hard]

What about a blockage in the master cylinder? or even the proportioning valve? that valve might be gone...

 

[bjoehandley]

My '98 does that some (no ABS, but it has Selec-Trac)when it damp out, but not as much as Mom's '87 Chevy Beauville F/S van was terrible at that. I could barely touch the brakes ond if it was damp the thing would lock up one of the front wheels, even at 5mph?!

 

[JJacobs]

leaky rear axle seals?