Installed a new CPP power booster, cylinder and proportioning valve on my 57 Chevy with disk/drum. Pedal pressure is great and calipers and cylinders stroke fine. Here's my issue... With the engine off I have a full firm pedal. Hold pressure on it no movement. As soon as I start the engine and get vacuum to the booster, the pedal drops about 1/2 way to the floor instantly (while holding foot pressure on the pedal). Pumping the pedal makes no difference. Stops fine, just not a lot of pedal. Have bled lines multiple times, adjusted rear drums. Any suggestions on what to check or where to start? Thanks
Hiya Sometimes there is some adjustment on the booster to raise or lower the pedal. I guess it's there to line up your brake and accelerator pedal. Have you checked it? I've got a TCI booster on my coupe and the weight of the pedal is enough to gently apply the brakes !! I had to fit a return spring to keep the pressure off the brakes from just the weight of the pedal. I think if the pedal came with the CrPP kit is it the right size ? Or is it your original pedal?
The pedal should drop somewhat, agreed. I would do some adjusting on the rod out to the booster, keep track of what you change.
Thanks to everyone that answered. I think I have it working. When I installed everything, I bled the lines several times. Even used a pressure bleeder. Decided to do it again. Bled the old school way. Had a friend pump it up, hold it while I opened the bleeder, repeat, etc. Nothing in the rear except clear fluid after a couple dozen vents. Moved to the front disks. Nothing but clear fluid for about a dozen times, then a huge slug of bubbles. All in all, ran about a quart of fluid through the lines. No air visible. Started the car up, the pedal drops an inch or less, stops great. Think all is good! At least for now. Sent from my iPhone using Tapatalk
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