replaced the mastercylinder have bled the brakes thre or four times my pedal is hard and barely stps the car
You may have a defective check valve at booster. . You should have 15 or more inches of vacuum to the booster at idle. Check at both sides of the check valve.Power assist is dependant on vacuum supply and the functioning of the brake booster. First check manifold vacuum to the booster. Then perform this test: With engine off, depress brake pedal three times, and should have assist, then start engine. The pedal should drop. If it fails these tests, the brake booster is defective. There are other reasons for a hard pedal other than lack of assist such as a restriction in the brake system (usually brake hoses) or frozen stuck calipers. It appears you have a defective brake booster that can be returned under warranty. If your vacuum reading is good, first I would check to see if you are getting fluid pressure out the bleeders and check movement of the caliper pistons. If all appears good, replace the defective booster.
What was the reason you replaced the master cylinder?
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