Re: '53 Cavalier brake problem

Posted by BH On 2010/1/8 23:18:58

scottie -

If the pedal travel became "stiff as a board", I'm not so sure that it was from a loss of vacuum.

The vacuum section of the Treadle-Vac is a only a power "assist". In the event of a total loss of vacuum, all you lose is that assist. With else everything in proper working order, the pedal should still move the push rod and plunger, which will quickly bottom out against the vacuum piston plate, which is in direct contact with the hydraulic plunger. Granted, it does take a bit more more effort to stop, then - even compared to a vehicle with standard (non-power) brakes. Pump the brake pedal several times in your car with engine not running, and you'll get a comparative feel for it.

Not long after I purchased my first '56 Patrician, I lost power assist one day, but had no trouble coming to a complete and safe stop. Turns out the internal vacuum hose had slipped off the fitting that passes though the shell, but that wasn't the whole problem. Someone had previously replaced that hose with a piece of common fuel hose. A core from offsite storage provided an original formed/molded hose, which was more like vacuum hose on steroids. Never had the problem again.

In the case of your '53, I have to wonder if something prevented either the push rod, vacuum piston, or hydraulic plunger from moving through its full range of travel. What's weird is that it was a transient event.

Of course, it wouldn't hurt to check the vacuum supply hoses, reservoir, check valve, and even the pedal assembly, first, but you're probably gonna have to look deeper.