1964 Brake Pedal Hissing?! NEW Booster and Dual Master

[Lee]

While in the car is running and I repeatedly step on the brake there is a hissing every time I press on it and I cant feel any pressure build up.

When I turn the car off and then press the brake pedal, the hissing continually gets less and less and after 6 or 7 presses, I have good pressure on the pedal.

Based on these statements from your original post, I don’t believe that any of the lines you may find disconnected are the cause of your “noise”. And it may just have to do with the non-stock booster you are using. You WILL hear air rushing into the driver side, especially with the engine off, and you will hear it every time you step on the brake until the vacuum reservoir is depleted. To me, it sounds more like a low “whoosh”, rather than a hiss, but it is just atmospheric pressure entering the pressurized side of the booster.

You should NOT hear the noise with steady pressure on the pedal, or with no pressure on the pedal. If you do, then there is indeed a leak. It should also hold vacuum in the reservoir for at least several minutes after you shut off the engine. But whatever we call the noise of inrushing air to the drivers side of the booster…it is normal.

[MattSWE]

Thank you for the responses, i have determined that the booster and master are probablly ok even though both are aftermarket and that more than likely i need the brakes adjusted/wheel cylinders checked. It feels like the brakes should engage way sooner and have alot more stopping power.

I spoke with cpp and the whoosh is normal and no o-rings are needed due to being inside the booster for seal.

[MattSWE]

Just wanted to give everyone an update on the brake situation.

I check all wheel cylinders and the front passenger cylinder is leaking under the rubber boot.

Also, all my brake shoes are pretty thin and all the inner shoes have a groove cut in the middle of them and does not look normal.

what would cause this?

[Dan Szwarc]

The groove in the middle is normal. It’s likely there as a wear indicator. If you still see it, it’s not worn all the way.

[Lee]

Agree with Dan, I've seen this over the years on old brakes I've changed out. It bears mentioning, if you don't know how old the linings are, assume that the dust inside the drums contain asbestos. Just try to clean things up with mineral spirits or brake cleaner, and don't use compressed air. Maybe use a dust mask or respirator. It's harmless unless it's inhaled.

[TonyC]

I second Lee's caveat. Many owners will not even think about examining the rear brakes, meaning the linings there could possibly be made of asbestos before that substance was nixed due to its danger to human health. Use a good mask to spray everything off.

I recently had to do a maintenance job on Frankenstein's rear brakes when I felt a disconcerting grab in the first few minutes of running. It had been four years since I was even inside those drums, and and there was quite a dust buildup in them. Spraying down with brake-cleaner cured the problem. Side note: I had replaced the linings four years ago, so I know my brakes are devoid of asbestos.

---Tony

[Goldstar]

Great stuff, boys. Thanks for the info!
Peter