Brake pressure?
Thread Starter
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Senior User
Joined: Dec 2004
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Brake pressure?
Hello
Iv'e completed my dics brakes on my 65 mercury. I installed the master cylinder with power brake booster and it all works but........ It seems that there is not enough pedal to travel so I welded up a longer pushrod for the brakes. Now the pedal dosen't hit the floor but still not enough pressure. I seems like my master cylinder is weak and not creating enough pressure to stop good. It does stop but not good. Iv'e check for leakes, bled the brakes thoroughly, adjusted the wheel cylinders up. Is it possible to have a weak master cylinder. It's got all new lines. Could have I put too much line in the system so pressure dosen't build up. I put charger brake hoses in the front too but they seem to work fine. My master cylinder dosen't build enough pressure to stop good. Do I need a larger master cylinder like one out of a 250 for more pressure. If you pump the brakes once then put the pedal too the floor the truck will stop instantly. If I hold the brakes down the pressure will be lost but the brakes are still working non-theless. Yes I know, sounds like a bleeding problem but its bled really well. Did anybody have this problem?
Iv'e completed my dics brakes on my 65 mercury. I installed the master cylinder with power brake booster and it all works but........ It seems that there is not enough pedal to travel so I welded up a longer pushrod for the brakes. Now the pedal dosen't hit the floor but still not enough pressure. I seems like my master cylinder is weak and not creating enough pressure to stop good. It does stop but not good. Iv'e check for leakes, bled the brakes thoroughly, adjusted the wheel cylinders up. Is it possible to have a weak master cylinder. It's got all new lines. Could have I put too much line in the system so pressure dosen't build up. I put charger brake hoses in the front too but they seem to work fine. My master cylinder dosen't build enough pressure to stop good. Do I need a larger master cylinder like one out of a 250 for more pressure. If you pump the brakes once then put the pedal too the floor the truck will stop instantly. If I hold the brakes down the pressure will be lost but the brakes are still working non-theless. Yes I know, sounds like a bleeding problem but its bled really well. Did anybody have this problem?
Posting Guru
Joined: Jul 2003
Posts: 2,232
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From: Colville, Washington
If you lose pressure while holding the pedal down, there is either a leak in a fluid line or a faulty master cylinder or booster. Can you hear any hissing or pssst type noise from the booster immediately after turning the engine off?
Thread Starter
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Senior User
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Putt your onto somthing.
Hello
Putt there is a hissing noise as soon as you turn the truck off. What does this mean. Is the booster toast. I checked all the lines again.... no leaks anywhere. But there is definatly a hissing noise in the booster. Explain what this is.
Putt there is a hissing noise as soon as you turn the truck off. What does this mean. Is the booster toast. I checked all the lines again.... no leaks anywhere. But there is definatly a hissing noise in the booster. Explain what this is.
Posting Guru
Joined: Jul 2003
Posts: 2,232
Likes: 1
From: Colville, Washington
The hissing is the vacuum leaking out of the vacuum chamber in the booster. It might be a bad check valve(where the vacuum hose hooks) at the booster, but it is probably a leaking diaphragm.
