Vali68
Well-Known Member
We had the master cylinder replaced about 7 years ago on this 68 valiant. How hard is it to replace the seal between the master cylinder and the diaphragm that fits in the wall of the car?
Brake master possible leak
- Thread starter Vali68
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AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Again, Huh?
BillGrissom
Well-Known Member
Photos would sure help, or poke around in Google Images to find the correct terms for parts.
If "diaphragm" means the "vacuum booster", there is no seal there. Indeed, there is a gap in the plastic at the bottom to equalize pressure or perhaps drain leaking fluid. But in A-bodies the booster doesn't bolt direct to the firewall, so ditto the "huh".
If you mean a manual brake car and the thin white foam between it and the firewall, that is just a dust seal and I recall referred to as "paint seal" or such. You can buy a set of foam from places like DMC, or just cut out yourself (like I do) from the white foam bags in retail electronics packaging.
If "diaphragm" means the "vacuum booster", there is no seal there. Indeed, there is a gap in the plastic at the bottom to equalize pressure or perhaps drain leaking fluid. But in A-bodies the booster doesn't bolt direct to the firewall, so ditto the "huh".
If you mean a manual brake car and the thin white foam between it and the firewall, that is just a dust seal and I recall referred to as "paint seal" or such. You can buy a set of foam from places like DMC, or just cut out yourself (like I do) from the white foam bags in retail electronics packaging.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
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Thanks Bill.Youre so tactful.
Vali68
Well-Known Member
I was referring to the master cylinder and it's bolted onto the brake booster. I thought there maybe a seal there. But maybe I'm wrong.
BillGrissom
Well-Known Member
The photo helps a lot. Shouldn't be a seal. I have a similar Bendix booster on my 65 Newport. I have also had Midland-Ross boosters (V-band clamp). All have a plastic piece with a "drain slot?" at the bottom. You can unbolt the MC and pull away slightly to see, won't hurt anything.
You are correct that some cars do have a vacuum seal between MC and booster. My M-B are like that w/ a thin Girling booster. The boosters on my minivans are similar thin, pancake type. The boosters on our cars have an internal bellows around the output rod that seals vacuum. I suspect all thin ones don't and thus must use the MC to seal vacuum at the output hole.
You are correct that some cars do have a vacuum seal between MC and booster. My M-B are like that w/ a thin Girling booster. The boosters on my minivans are similar thin, pancake type. The boosters on our cars have an internal bellows around the output rod that seals vacuum. I suspect all thin ones don't and thus must use the MC to seal vacuum at the output hole.
TrailBeast
AKA Mopars4us on Youtube
And the short version is that if you have fluid coming out from between them, your master cylinder is leaking fluid past it's seals and needs to be replaced.
(Preferably before it ends up eating up the booster rubber)
(Preferably before it ends up eating up the booster rubber)
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