[RocktimusPryme]

Originally Posted by mgarblik

Well I can partially tell you what your looking at! Your not looking at a 62 factory booster, Moraine or Bendix. The MC also is off something slightly newer, 1963-1966. 1967 would be the first year for a dual MC, and that is a single. The hissing noise is about a 90% likely defective air control valve in the booster and not the diaphragm itself. It is mostly a plastic part and after 60+ years is likely cracked somewhere internally. Basically, foot off the pedal, somehow vacuum is making it's way into the valve and exhausting inside the car. If the diaphragm was cut or punctured, the pedal would be hard and you would hear vacuum in the car all the time foot on or off the pedal and it would idle rough. If you still have power assist, you can probably drive it a little with this leak, especially if it seals when the brakes are applied. The 61-62 power brake booster is unique and pretty weird. The MC piston is actually a part of the booster and only the seals are serviced. It's kind of semi-integral. Really doesn't interchange with anything modern without replacing MC and Booster. For a lowest cost repair, I would try to get the system bled and see how it feels as is. Overall the booster/MC looks like 63-66.

That is all important because if I found my MC is bad and I bought a new one for a 62 only to find it didn't fit that booster I would have been annoyed. This is why Im asking these questions. I wouldn't have guessed a 63-66 would have had that plug port in it.

Is that internal air control valve repairable? I might opt for that if there was a cheap kit to fix it and just keep matching parts that work together, together.