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Discussion Starter #1
Hi everyone!

Just got a new toy, but it will need some attention. So, I already have a question in case someone has any idea what is going on.

I had to replace a brake power booster. It works much better, but when I step on the brake and hold it down it falls all the way to the floor and you can hear what sounds like a vacuum leak. I checked for brake fluid leak and cannot find any. Vacum from the intake manifold is ok. Only thing I can think of is that the push rod from the power booster is not adjusted corectly. Any suggestions.

Thanks a lot,

Mirko
 

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Sounds to me like to booster ain't working right to me.

I had that happen to a non-mustang I own. Kept getting a whooshing sound from the brakes, got progressively louder, then one day, no brakes. Turned out the booster had failed.

If you replaced the booster, maybe it didn't get put back right-my other car had a gasket between the booster and the MC that was critical. Maybe the hose is leaking, the check valve is bad or ???

The whooshing sound is not good I don't think. Check it out before you get surprised (went right through and intersection with no brakes) like I did.

J. Boggs
 

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If it pumps up and holds but slowlt lets your foot to the floor, your m/c is done. Be sure to properly bench bleed it before you install the new one or the problem could remain.
 

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I concure, it's the master cylinder. OR you have a brake fluid leak somewhere in the system, such as at a wheel cylinder or brake hose, but that should be easy to spot.

The only thing that can cause the pedal to slowly fall to the floor is if the hydraulics cannot hold the pressure.

If the booster was bad, it would be very difficult to push the pedal down enough to stop the car, like with all your weight. But there would still be a solid pedal. The pushrod really only affects when the brakes engage, since it's the link between the pedal and the master cylinder.
 

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Welcome! Where in Ca are you located?
It sounds like your problem is not vaccumm. I think the other posters are right, get a new M/C first. I got one at Autozone for about $19.
 
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Discussion Starter #8
Thanks everyone. I appreciate your help. Master Cilinder is actually new, and was bled on the bench. Only thing that is not new is the proportioning valve.

Grabbrtblue, i am from Mountain View,CA.
 

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Is it actually a NEW master cylinder, or a REBUILT master cylinder? If it's the latter then go get another and try that one. I work at Kragen, and while our rebuilt M/Cs are very good quality, they have the highest one-time comeback rate out of any other part!
 

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Is it actually a NEW master cylinder, or a REBUILT master cylinder? If it's the latter then go get another and try that one. I work at Kragen, and while our rebuilt M/Cs are very good quality, they have the highest one-time comeback rate out of any other part!
 
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