Hi all,

Just finished a brake job on my son's '83 245: master cylinder, front calipers and rotors and pads. Bench bled the master, then bled the whole system. Lots of pedal, all as it should be.

When we start the car, the pedal disappears. I'm suspecting something with the booster, but I thought that a faulty booster still left you with manual brakes.

Any ideas?

 

What do you mean by the "pedal disappears"? Goes light and softer? If so, that's what vacuum boosted brakes do, they lighten pedal effort by applying an assisting force to the master cylinder.

Regards, Andrew.

 

You can verify the booster/servo check valve, vacuum hose to booster and junction brake box....

 

Did you bleed the brakes correctly? Does the brake light come on the dash? Very finicky system that must be bled correctly. Don't know what bleeding method you used, but unless the rules on bleeding are followed to the letter, you cannot achieve results. Also make sure you bleed at each valve(2 per caliper)

This works:
Best to use a power bleeder attached to the master cylinder
Fill system with fluid. Start at the wheel farthest from the master cylinder (not just those worked on), pump the pedal until hard or at least 7 times if it does not harden. Then open bleeder while someone keeps pressure on pedal. Close bleeder. Lift pedal and repeat process until no air comes from bleeder. Check level EVERY THREE ATTEMPTS. If it is ever to the bottom or the pedal was allowed to move up while bleeding, you must start entire process over from the beginning. Continue to the next furthest from master cylinder. Repeat sequence. If fluid level ever falls to bottom, start over at first wheel.

This works 100% of time. If you don't have good pedal, you have a different problem.