Re: 57 Clipper - Break Issue

Posted by HH56 on 2020/6/13 11:28:03
There should be a residual (check) valve at the end of the master to prevent fluid draining back into the reservoir. When the brakes are applied the master cylinder piston moves a control piston in the booster to start the vacuum assist. The fluid from the master is also passed into the slave cylinder and brake lines to provide initial brake action. As the vacuum starts moving the power piston to apply more power another check valve in the power piston is supposed to trap the fluid in the slave cylinder so the vacuum assist is providing the power. Perhaps one or both of the valves are not working.

No idea of the specs for the master cylinder residual valve but probably 2-5psi. An external residual valve in the line between the master and booster might do the job if the master valve has failed or is missing. I would be careful to keep the valve at a low value so as not to provide so much valve resistance fluid could not easily return to the master and reservoir via spring pressure from the wheels when brakes are released. If not enough fluid is returned brakes would be a candidate for locking up or being extremely sensitive as they were repeatedly applied, each time adding more fluid and filling lines and wheel cylinders.

Here are a couple of scans from the 56 Stude manual. Your 57 Clipper was a facelifted 56 President model so brakes should be the same as the Stude manual details.

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