Guest klinc Posted October 17, 2008 Share Posted October 17, 2008 Im trying to bleed the brakes and I have a hissing noise coming from the master cylinder. i found a leak from the cap only. so I order 2 new ones. still hear noise. Is that common? any help would be great Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 17, 2008 Share Posted October 17, 2008 Probably a hole in the diaphragm. That means you need a new booster. Does the booster hold vacuum when the car is off? Quote Link to comment Share on other sites More sharing options...
Guest klinc Posted October 18, 2008 Share Posted October 18, 2008 after a few pumps it does. when i test drove it i can stop with a few pumps. Quote Link to comment Share on other sites More sharing options...
JMortensen Posted October 18, 2008 Share Posted October 18, 2008 After a few pumps??? Sounds like you need a new brake master cylinder. The test for that is to very slowly put pressure on the brake pedal. If it goes to the floor, then your master is bad. Once that is fixed then you can check the booster. The idea is that the booster should hold vacuum after the car is turned off, so if your engine dies for some reason when you're driving you still have several power assisted stops before you run out of power brakes. If you step on the brake with the car off and the pedal feels rock hard, that is an indication that you're losing the vacuum in the booster. You can't really do that test if the master is bad. It is tough to diagnose problems over the internet but I think in all likelihood you need a master cylinder and a booster. Quote Link to comment Share on other sites More sharing options...
woldson Posted October 19, 2008 Share Posted October 19, 2008 Check for leaking out of the rear of the master. If it is leaking in the booster, it is probably just a matter of time before the booster goes bad, if it is OK now. Quote Link to comment Share on other sites More sharing options...
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