power brake question
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Senior User
Joined: Mar 2002
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From: MOYOCK NC
power brake question
Just wanted to know if anyone else has had this problem with the eng not running i have a real firm pedal but when i start it the pedal gets real spongy and the travel is alot greater than when it is off i have disks up front and drums in the back and of course the right proportioning valve i got the booster from the junkyard and i do have a new master cyl so im thinking i have a bad power booster any one know of any other checks i can without throwing 100$ for a new power booster?
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Experience is the name everyone gives to their mistakes.— Oscar Wilde
gee ooh
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Experience is the name everyone gives to their mistakes.— Oscar Wilde
gee ooh
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Joined: Dec 2004
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From: Cedar Rapids, IA
fordgo:
The power booster works off of the engine vaccuum. Most are designed to give you 3 pedal pumps of boost after the engine stops running before they stop giving power assist. If you are getting a firm pedal the first pump after you shut the engine off I would say that the vaccuum valve that "TBucketJack" mentioned is bad. As far as your spongy pedal goes... when the engine is running the booster is assiting your pedal pressure. The pedal should travel farther for the force applied than is does when the booster is not assisting. This does not mean that the pedal should be excessively spongy or that the pedal should travel anywhere near the floor. If it does one of these things then you need to bleed your brakes again and/or look for leaking, worn out or mis-assembled break part elsewhere.
The power booster works off of the engine vaccuum. Most are designed to give you 3 pedal pumps of boost after the engine stops running before they stop giving power assist. If you are getting a firm pedal the first pump after you shut the engine off I would say that the vaccuum valve that "TBucketJack" mentioned is bad. As far as your spongy pedal goes... when the engine is running the booster is assiting your pedal pressure. The pedal should travel farther for the force applied than is does when the booster is not assisting. This does not mean that the pedal should be excessively spongy or that the pedal should travel anywhere near the floor. If it does one of these things then you need to bleed your brakes again and/or look for leaking, worn out or mis-assembled break part elsewhere.
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From: MOYOCK NC
Thanks guys
Ive already bleed them both ways using a mity mite vac pump bleeder and the old fashion way of holding the pedal and cracking the bleeders like i said it was a junkyard power booster and im not what shape it is in i was just wondering if anyone had run across a similiar problem oh well
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Experience is the name everyone gives to their mistakes.— Oscar Wilde
gee ooh
Ive already bleed them both ways using a mity mite vac pump bleeder and the old fashion way of holding the pedal and cracking the bleeders like i said it was a junkyard power booster and im not what shape it is in i was just wondering if anyone had run across a similiar problem oh well
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Experience is the name everyone gives to their mistakes.— Oscar Wilde
gee ooh
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Joined: Sep 2004
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From: Near Fresno, California
I don't believe that your spongy brakes are caused by the booster - it sure sounds to me like it is working. It is giving you more pressure in your brake lines than you had without it. How does your truck stop with it connected compared to when it is disconnected?
Did you replace all your rubber lines? Old ones can swell under pressure.
Did you replace all your rubber lines? Old ones can swell under pressure.
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Joined: Feb 2005
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From: Upper Left Coast
Locking brakes
My 54-55 shop manual indicates that:
"Locked brakes may be due to a restricted by-pass port in the master cylinder, by improperly adjusted pedal linkage, or by swollen piston cups, or by dirt in the brake fluid".
They go on to suggest opening a bleeder screw to release the brakes.
Then they suggest adjusting the pedal free travel, replacing the master cyl piston and cup assembly, and/or bleeding the system.
"Locked brakes may be due to a restricted by-pass port in the master cylinder, by improperly adjusted pedal linkage, or by swollen piston cups, or by dirt in the brake fluid".
They go on to suggest opening a bleeder screw to release the brakes.
Then they suggest adjusting the pedal free travel, replacing the master cyl piston and cup assembly, and/or bleeding the system.
Originally Posted by reamer
My '48 wit actory PB has an oppisite problem, Press teh pedal and the brakes lock and stay locked!
I have to pull the vac line to get the brakes to release. Clues on this one??
Reamer
I have to pull the vac line to get the brakes to release. Clues on this one??
Reamer
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