I'm having some wierd brake problems after my car sat for about 6 months waiting for its new motor. The motor's in, running good (except some cold start issues), but now the brakes are screwey. They just go mushy all of a sudden, then they come back when they want to.

car: 1998 accord 4 cylinder (turbo'd)

i went through the "brake booster tests" on pg 19-17 of the helms, once cold, once after a test drive.

the test drive was weird, brakes were ok, then BAD, then ok, went to dunkins for a coffee, brakes were MISSING in the parking lot the whole time (right to the floor), driving down the road it brakes fine again. STRANGE.

functional test:
1: press pedal several times, then press & hold. if pedal sinks, something's leaking or mc bad.

result: hot & cold, doesn't sink at all

2: start engine w/ pedal pressed, if pedal sinks slightly vacuum booster is normal

result: before test drive, sinks slightly. after test drive, sinks to the floor when started.

3: w/ engine running apply brake slightly, if brake pedal sinks more than 3/8" in 3 minutes MC is bad

result: cold, no sinking. after test drive, sinks slowly to floor

leak test:
1: press brake pedal w/ engine running, then stop engine. if pedal rises at all within 30 seconds booster bad

result: cold, no problem no pedal rise. after test drive, once pedal is pumped up and held, motor shut off, no pedal rise

2: with engine stopped press brakes several times. 1st time should be low, pedal height will gradually rise each time after

result: cold & hot, works as expected.


sounds to me like it's probably the master cylinder, especially since it's an intermittent problem. I'm looking for additional experienced opinions, thanks!! -B

edit: no visible leaks in the system either, and MC fluid level does not seem to be changing.

 

update: bled the brakes, they worked ok for a little while and now they're screwy again. leaning towards master cylinder.

if pressed hard when the car's running the pedal will go all the way to the floor, then when I let it up the car idles up a few 100 rpms, thinking this is the vacuum reservoir refilling itself?