Date registered: Jul 2009
Vehicle: 1964 Mercedes 220Sb
Location: Muskegon, Michigan
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Simple way to test your booster is pump the brake pedal with the car off until the vacuum is dissipated, the pedal should get hard after 3-5 pumps. Then while holding the brake pedal start the car, the pedal should drop as the car starts.
If the pedal never gets stiff or doesn't drop when the engine is start you have a booster leak. They can leak from the main seal, the boot in the interior, or where the master cylinder is connected.
When my booster was bad it actually stalled the engine when I hit the brake pedal.
Does your brake fluid level go down, or do you keep the same amount of fluid? (if your losing fluid its a hydraulic problem, if not its vacuum or internal master cylinder)
Was the replacement master cylinder new or used?
Most cars won't run with a vacuum leak that big, if your gonna run it with the vacuum disconnected get a big bolt (one where the head is bigger then the hose opening) and a hose clamp and put the bolt in the hose and clamp the hose around it.
Last edited by tgikal; 01-13-2010 at 04:50 AM.