I recently had a problem with my brakes, they were kind of spongy, and the brake indicator light was on, so I replaced the MC, in the process I noticed the booster looked bad (it had brake fluid leaking from it) so I replaced it too.
Soon after that, the brakes would drag after a few minutes of driving (the pedal would build pressure and become hard to push, at first if I would pull over and wait, the pressure would ease up enough for me to continue, I RTFM and thought it might be the MC, but since I needed to save some time, I took it to a brake shop, I then proceeded to pay for them to fix everything else that was wrong with the brake system, incl. rebuild calipers, machine rotors/drums, install new hardware/pads on front/rear brakes.
I drove it out of the shop, and immediately had the same problem. They then proceeded to replace the booster (luckily it has a lifetime warranty) They said that the adjustment pin was broken. It took the mechanic 6 hours to replace the booster, and when I drove it off the lot, the brakes locked worse than before, the rotors were actually glowing when I stopped.
They then replaced the MC (New not reman.) which they did free of charge since I had the corporate office involved at this point. same thing.
And finally they replaced the check valve, but the brakes are still locking.

Is there anything they may have screwed up on, any error they could have made, anything I could have missed? I don't have complete confidence that they did everything right.

Please wrack your brains, I'm totally stumped on this one.

Any suggestions appreciated no matter how crazy.


Modified by SpeedKnight at 7:16 PM 7/9/2003

 

There is a procedure to adjust the pre-load on the MC, sounds like it is too tight, making the brakes drag. Hard to believe it happens with three or four different MC's though.

Tom

 

make sure the booster check valve is oriented correctly. If it's facing the wrong way, the booster will hinder rather than assist brake actuation.

You should be able to blow through it one way only. The side which you can blow through should be the side that leads to the m/c.

 

Yeah, I would say adjust the preload on the booster - use the adjustment stud that connects to the brake pedal inside the car. I'd also point to the check valve, which was already noted

 

Its your master cylinder. My friend had this problem on his 89 Rex... took it to the shop multiple times... he went through a new set of Green Stuff pads and every other part in the brake system before he replaced the cylinder... and then it worked!

 

check valve, has to be

 

Thanks for the advice so far everyone.
Here are a couple more things I thought of that may help us pin it down.
-They have been adjusting the booster on the MC side
-When he installed the booster, the "mechanic" placed the bracket that hooks to the brake pedal on the booster and wedged it into place.

 

I would have to say it is the actator rod thingy. When you build up preassure the brake assist is causing the slight preassure to be increased, locking up the brakes. I can't remember the correct name for it but it is the rod that transfers the movement of the pedal throught the booster to the MC. It looks like a PITA to adjust in the shop manual.

-Dustin

 

Answer:

The brake shop sucks. I can't believe they are having such a hard problem with your car. Brakes are not that hard to work on and figure out.

Go buy a Helm's and it shows you the way to test the entire brake system and how to adjust everything correctly. It seems pretty obvious to me that your mechanic place doens't kow the correct way to adjust the MC and booster. It sounds like they are trying to adjust it until it works and what they really need is a friggen book.

 

One really *strange* problem I have dealt with before is :
Where the caliper mounts to the caliper bracket,
The "pins" the caliper-body bolt to are supposed to "float"..{ie: slide in and out without resistance}
if they are seized in place;
the caliper will not be able to float/move around and it will hold pressure
against the pads and drag against the rotor..
When diagnosing; it seemed like the brake booster or master cylinder was losing pressure as the brake pedal would fall slightly..

 

Thanks a million for the suggestions all, especially that I should get a Helm's manual and do it my damn self.

Since every piece of the brake system is under warranty, they're doing all this stuff for free. Any super crazy, super obvious answers are much appreciated. I relayed every suggestion so far to the tech, even the Helm's manual.