Re: Lack of Power Brake Assist (was Plate for 56 pat gas tank)

Posted by BH On 2008/5/29 7:36:53

In every car I've ever owned that was equipped with (vacuum) power brakes, I could easily check for a lack of power assist from the driver's seat, as follows:

1) With the engine off, pump the brake pedal a few times to make sure the vacuum reserve is exhausted.

2) Release the pedal completely, then re-apply foot pressure and hold.

3) Start the engine. Vacuum will build quickly, and you should feel the pedal drop away a slighlty (under foot pressure). If not, then you have no power assist.

To find the cause, the first step is to remove the hose from the check valve at the back of the carb (with the engine running) and inspect for the presence of vacuum at the valve. Then, work your way upstream with inspection to the tee at the booster and the vacuum reservoir (tank).

If you can eliminate vacuum source and external leaks as the problem, then there must be an internal problem with the booster itself. Something may have been overlooked in the rebuild process, but check the air inlet filter on the booster to make sure it isn't clogged BEFORE you remove the thing and ship it back.

The Bendix TreadleVac (aka - BTV) is not nearly so complicated (or deadly) as some people make it out to be, but there are some parts that are not readily available to the public at-large - especially with the booster internals. Reputable rebuilders may have repro'd them, but will only sell them as part of their repair service.

Caveat - if you're wanting your unit rebuilt and returned, my advice is to stay away from "middlemen" who simply sell on an exchange basis, but deal directly with a competent rebuilder. (Hopefully, owners will share their favorable experiences by adding such suppliers to BigKev's Packard Directory.)