O/T late model - I keep losing my brakes!

[hillbillyhellcat]

I don't know where else to turn in regards to this car. My winter beater is a 1990 Subaru Justy, a little 3 cyl import. I was driving it few weeks ago and the brakes failed, I mean nothing, then they came back after I pumped them up a bit. I had just had it inspected and had replaced a caliper. I checked out the master cyl which seemed to be bad so I replaced it. It did it again and I took it to a garage, where they determined it to have a bad new master cyl. They replaced it again. I lost the brakes again today on the way home from the garage. There are no fluid leaks anywhere as the canister is always full. The brakes are all good, front are new, no rotted lines, no nothing. I am clueless. We thought there might be something wrong with the brake booster, so I unhooked it and plugged it off. The pedal feels a bit better? I have never heard of a booster giving TOO MUCH power assist that the pedal goes to the floor.... Any ideas? I don't want to junk this little car, it saves my old cars in the winter! http://www.jalopyjournal.com/ubbthreads/images/graemlins/confused.gif

[Flexicoker]

it could be that the stock rubber lines are kind of old and swelling under the pressure, just an idea.

[LIMEY]

Just a shot in the dark but i've seen a bad front wheel bearing give simular symptoms, asuming its disc's up front!
The excessive movement in the bearing causing the disc to push the pad/piston back in the caliper, pumping the pedal will bring the brakes back just like when you have fitted new pads.
Seems like you covered all other aspects thats what made me think of this.

[deuce]

my girl friend had a '79 corvette that did the exact thing. finally traced the problem to bad caliper piston seals. they were not leaking any fluid, but as they went back and forth they were letting air into the cylinder and causing very mushy brakes. we replaced all of the piston seals and cured the problem. i sure am glad she sold the car.