alexrains

Can somebody please enlighten me on the existence of a gasket between the master cylinder and the brake booster on a 1966 442?

Engine idles slightly (!) rougher, when not stepping hard on the brake (then perfect).

All vacuum lines are definitely tight but there could be a loss, as master and booster just "sit" metal on metal.

Thx, Alex.

MDchanic

I believe there is generally a paper gasket between the booster and the firewall, but no gasket between the m/c and the booster.

- Eric

joe_padavano

Actually, there is, and it does seal the front vacuum chamber of the booster. This seal is very difficult to get. The only sources for new ones I've found are the Corvette repro houses, and thus they are priced accordingly.

Note that there are two styles, depending on year, the flat ones and the cupped ones.

MDchanic

I was thinking of a flat gasket between the two mating flanges - guess I was thinking too narrowly.

- Eric

oldcutlass

Nope just the cup.

alexrains

Eric: that was my mechanic's opinion also, but the "hard on brake thing" made me think.

Joe: will order all, as it gets on my nerves and shipping to my country takes ages...

Thank you both! Really appreciate how fast this forum is.
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jfb

I experienced this myself so maybe you should check it also. check around the area when the car is running and I mean the master to vacuum booster for a vacuum leak the booster might be bad. I went through this before on mine. check with a vacuum gauge also for fluctuations of vacuum levels.

oldcutlass

I just changed my booster because it was leaking. When I pulled it out I found that the assembly had broken on the rear allowing the push rod to flop around inside the power booster that created a small leak. Push on the pedal and the engine would drop 200 rpm, release and they went back up.