I just replaced my rear calipers, pads, and rotors. The pedal was low after I bled the system, one thing i didn't do was do the sequence for a 1990 w/ ABS, I did the normal bleeding sequence, R/R, L/R, R/F, L/F. I took it back into my garage today and gravity bled new fluid through the system until new fluid came out of every bleeder and it was good while i drove home, which was 20 miles, then to my friends house which was 15 miles, right before i parked it i thought it was getting a little soft, then when i left about 3 hours later the pedal was to the floor. I have not idea what is causing this, the master cylinder isn't losing fluid, there is no fluid behind it when i took it off. I don't think it's a brake booster, but then i don't really know what all the symptons of a bad booster are. Any help would be greatly appreciated. Thanks. My car is a 1990 SE w/ ABS.

 

master cylinder is most likely the culprit. it could be leaking (even though it dont look like it). if it was a blown line you would know right away. if the master cylinder isnt completely gone yet it might have the symptoms you are describing. so replace that as a start and g/l. no brakes sux (especially at 145mph Doh)

 

Exactly, not all master cylinder leak when they are bad. And sometimes they leak inside the car instead of down the booster. Also, the seals internally may go bad causing no pressure to build. i.e. low pedal

Since I dont have ABS I dont know how critical it is to follow the ABS bleeding procedure, but I would try it before anything else. At least that's free. Also what was the reason you changed the calipers to begin with, was it for this same reason?

 

Well I took her into my work today and tried bleeding everything, still didn't work, but when I was driving it around i locked it up, but only the wheels that locked up were the L/F, and R/R so that pretty much was a dead giveaway that one of the seals was bad, so I got a master cylinder and pressure bled the system in sequence and seems to be working good for now......I don't want to speak too soon. Thanks for all your help.