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brake pedal to the floor

N nazgulMember
hi all,

first thanks for the help regarding my prior brake freezing up problem. a shortened pushrod seems to have fixed the problem. (but maybe not, because of the below)

now, an opposite problem has occurred. after breaking to a stop or to a greatly reduced speed, the pedal will slowly travel to the floor without any additional braking action occuring. seems not to happen all the time but is dependent on how long the pedal is depressed. the longer depressed the more certain the pedal will continue it downward path.

without the engine running, application of brake pedal pressure produces a hissing sound of air escaping in the area of the m/c-brake-booster. application of a soap solution did not reveal the source of the hissing sound.

the prior owner of this vehicle had posted a similar problem of pedal to the floor, the system was professionally rebuilt and had lines, calipers and the m/c replaced, the brake-booster was not replaced.

another thread with a similar pedal-to-the-metal problem suggests the brake-booster by reason of age may have developed a leak.

a leaky diaphram (small hole) would explain both the hissing noise and the pedal-down behavior.

am i correct in my diagosis??? thoughts or comments would be appreciated,

nazgul
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lf-tp2511lf-tp2511Member
Since so much has been rebuilt, and you hear the air hiss, I'd tend to agree with your diagnosis.

It could also be an internal MC leak, but that wouldn't explain the air noise.

I've heard most rebuilders will call the booster not-rebuildable. However, others have found more skilled mechanics that have done a rebuild.

Booster is a hard part to find new, but is probably still available as a Ferrari MC/booster combo, but at a large cost.

Larry
panteradougpanteradougMember
It is the booster. There is a company in Pittsburg that rebuilds your booster. They do the Mustang boosters for concours competion.
You are going to ask me who it is? Good question. I need to go and meditate to remember. Excuse me now. Ahume, ahume...this is going to take awhile.

Hint, most of the Mustang restoration shops use them, ask there. Cost? A couple of hundred US balloons. Maybe they will take dollars this time?
crazydavecrazydaveEFI Expert
Normally a slowly moving pedal, either clutch or brake means bad master. This is especially true if you are not loosing any fluid.

Next time it happens, try this. Stomp it hard and hold it with a lot of pressure. If it then is holding solid then it is likely a bad master. One of the first signs of a bad master is leakage at low pressure. When you hit the pedal hard, the pressure goes up and the seals hold. I one time had to drive by stabbing the clutch fast everytime I shifted to make the clutch work.
N nazgulMember
good evening all

while i was doing some final diagnostics on the brake booster and m/c before sending the booster in for a rebuild, i noticed that there was no gasket installed between the machined surface of the bolting plate of the m/c and the booster body. also, the m/c had a machined groove for, i believe, an o-ring. the o-ring also was not present.

this may sound like a real silly question, but shouldn't there be either a gasket or an o-ring, seems to me that there should be, especially when non-machined and machined are matched and a pressure tight fit is needed???

nazgul
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