just got done yesterday replacing the leaking master cylinder in my car which also took out the front seal on the brake booster which was leaking vacuum like crazy. brakes are completely stock just replaced front pads, rear shoes and drums. bench bled the master and bled it again on the car. no air in the lines or any leaks. got 20 in of vacuum at the line going to the brake booster at idle but the pedal is still pretty hard. a little better than it was before but still not great. it also seems like the more i drive it the better it gets. any ideas of what it could be? maybe the booster i got was bad??
brake problem
- Thread starter lmpbzkt492
- Start date
bill302
Active Member
FIXES FOR COMMON BRAKE PROBLEMS
following was copied from above link:
HARD BRAKE PEDAL Lack of power assist may be due to low engine vacuum, a leaky vacuum hose or a defective booster. Sometimes a faulty check valve will allow vacuum to bleed out of the booster causing a hard pedal when the brakes are applied. This condition can be diagnosed by starting the engine (to build vacuum), shutting it off, waiting four or five minutes, then trying the brakes to see if there is power assist. No assist means a new check valve is needed.
A quick way to check the vacuum booster is to pump the brake pedal several times with the engine off to bleed off any vacuum that may still be in the unit. Then hold your foot on the pedal and start the engine. If the booster is working, the amount of effort required to hold the pedal should drop and the pedal itself may depress slightly. If nothing happens and the vacuum connections to the booster unit are okay, a new booster is needed (the vacuum hose should be replaced, too).
heres another site that might help: http://mypage.direct.ca/k/kdomries/brakes.html
following was copied from above link:
HARD BRAKE PEDAL Lack of power assist may be due to low engine vacuum, a leaky vacuum hose or a defective booster. Sometimes a faulty check valve will allow vacuum to bleed out of the booster causing a hard pedal when the brakes are applied. This condition can be diagnosed by starting the engine (to build vacuum), shutting it off, waiting four or five minutes, then trying the brakes to see if there is power assist. No assist means a new check valve is needed.
A quick way to check the vacuum booster is to pump the brake pedal several times with the engine off to bleed off any vacuum that may still be in the unit. Then hold your foot on the pedal and start the engine. If the booster is working, the amount of effort required to hold the pedal should drop and the pedal itself may depress slightly. If nothing happens and the vacuum connections to the booster unit are okay, a new booster is needed (the vacuum hose should be replaced, too).
heres another site that might help: http://mypage.direct.ca/k/kdomries/brakes.html
turns out the booster i got was no good. threw another one in and everything was good. the only other problem i have now is that i think the master is no good either. car stops fine nice pedal but once you come to a stop maybe a second or two later with pressure on the pedal it slowly sinks to the floor
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