1994 ??? brake bleeding issue, sticking caliper Topic is solved

[kurts2]

Hi, I'm new to the forum and was hoping someone else has had this problem.

Here is the issue. for a few weeks now, the brake pedal will travel low prior to engaging intermittently. It usually happens after driving for around 30 min, and then it may start to work normal again in as little as 5 min. Sometimes it wont work normal again for hours.

Here are the symptoms:
No ABS or brake light.
Pumping will make the pedal grab higher but on next press it goes low again.
It does it with engine on or off (while failing).
There is no pedal fade (except during ABS lock up...see below) even after pumping.
In active ABS braking if the malfunction is present there is a slight difference...done on a dirt road lock up, the pedal seems to engage higher (as normal) but will fade down to lower point with the normal pulsing of the pedal being felt. When the fail isn't active, the pedal stays higher with the pulsing felt. I'm not sure if this is really a fade or just the longer travel combined with normal ABS function though.
Also oddly just prior to the malfunctions occurance, a slight squeal can be heard from one of the wheels...like a dragging brake, the sound can come from either the front or rear...it changes location. A slight press of the pedal seems to confirm its dragging brake. It can clear up or continue until malfunction disappears again.
Last thing of importance, the brakes work well...just low. Pushing hard results in solid braking.

So far have done a bleed and fluid change, no help so changed the master cylinder. That was no help either. Anyone else ever have this problem? I don't want to play guessing games/shotgun maintenance by throwing parts at it. If I was a gambler I'd change the ABS hydraulic module but really don't want to waste the thousands of dollars without some form of diagnostic proof.

Thanks for reading

Kurt

[kahl]

Has your brake fluid level been stable? How old or what is the condition of your brake hoses? The hose going from the hard line to the caliper. What is the condition of the vacuum hose from the intake manifold to the brake booster? Any sign of chaffing. Any sign of wetness on the booster where the master cylinder is attached? Any light sequel coming from the booster meaning the diaphragm is worn?

Trying to eliminate common items I have run into over the years.

[kurts2]

Thx for the reply, yes I forgot to mention the fluid level is good and there are no leaks. The vac system is good and the booster works well. I did change the master cylinder and there was no leak into the booster nor did the level ever go down prior to the change.

[Clemens]

Does the ABS light work at all? It should illuminate for a few seconds after turning on the ignition.
Also, what year is your car? The 96 and 97 and maybe later cars are prone to ABS module failure, thebearlier years with the metal enclosure ABS module are said to be very sturdy.

Check the wire harness to the module. Sometimes the insulation fails there. This might cause weird issues.

[kurts2]

Yes the ABS self test is good, light on for the self test then off...no codes at the A3 port (just 111 no faults present). Its an 94 with the metal enclosed enclosed module.

[kurts2]

Fixed! It had the outside rear left brake piston hanging intermittently and needed new pads all the way around.