Master cylinder w/ power booster

[gottabike]

OK, I'm in need of replacing the master cylinder looks like. I did front and back brakes and get no stopping power when the brakes warm up. The pedal goes to the floor. now i'm thinking its the cylinder. What do yall think? Also i know of the cylinder going bad but what about the booster? Could it be that as well. I know if i do the cylinder i'm gonna do it in the morning in front of the auto shop before they open and have them bleed it after. What do yall think is it one or the other or both??? Any help is much appriciated. Its a 92 PA Ultra SC

[wrightz28]

Was the problem occuring before you replaced everything?

[gottabike]

we got down to the wear indicators. I replaced the pads and shoes. then afterwards there is still no pressure in the pedal when you pump with the car on. The pedal goes straight to the floor. I worked on it a little last night and i could hear what sounded like air leaking out from the area where the cylinder and booster are. Could it maybe just be the vacuum system is off and needs to be reset?

[wrightz28]

Ok, no visable leaks? Loss of fluid? And all 4 wheels were bled?

[gottabike]

no fluid leaking, and havent bled them yet. I checked it sounds just like like air leaking when i pump the breaks. makes a bad suction sound like its getting a seal. It also seems to change from the weather like its about 75 now. here and they worked like normal all day long. but when it gets warm they drop straight to the floor and wont stop. i can press the pedal straight to the floor and the car will still roll forward.... What do yall think

[wrightz28]

Well, since you didn't bleed thme when you were done there's half the problem, the other half I would be suspected to beleive that you didn't open the master cyl. resivour, take some of the fluid out and releive the pressure when you reset the calipers. And if you reset them alot, then you may very well have wrecked the pistons in the master.

Always remember, open the cap, take about a 1/3 of the fluid out. Do your brake job. When done, examine the condition of the fluid, most the time, you can replenish, but if it's an older vehicle that has been fading it's brakes, it's a good idea to drain the system and bleed the system.

You may get lucky with just bleeding, but I wuld thuroughly test the car before putting it back in regular use. NO HARD STOPS THO!

[Jed Rule]

I believe in opening the caliper bleeder when compressing the piston. That bleeds off some of the muck instead of pushing it back into the ABS valves.