brake pedal spongy and drops to half way before resistance - Hot Rod Forum : Hotrodders Bulletin Board
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Old 07-18-2009, 10:53 PM
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brake pedal spongy and drops to half way before resistance

I recently bought a front disk brake conversion kit with a master cylinder and proportioning valve built in and non adjustable. The car is a 1967 firebird. The kits was for a 1967,8,9 camaro with 1 piston calipers. I bled all nearly a quart of fluid from the valves with a handheld pump. Overkill maybe but i get free brake fluid. There are no leaks. Pedal pressure was pretty good before starting engine. Master cylinder is full on both front and back reservoirs. 7" booster. Engine has 12# vacuum at idle. Has nine inch ford rear drums. Do these drums or brake cylinders require a different pressure or volume of fluid than gm drum brakes. I did not think this would cause a low brake pedal but possibly the back brakes to possibly lock up earlier than front. But the car stops ok but with much pedal travel and spongy feel. Thanks for the help. joe

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Old 07-20-2009, 10:26 PM
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Did you bench-bleed the master cylinder?
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Old 07-27-2009, 11:23 PM
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no i did not bleed the master cylinder but i did refill it many times while bleeding the wheels. I feel this would have bled the cylinder.

Also i noticed today that the rpms raise about 300 rpm when applying the brakes as if there is a vacuum leak when the brakes are pressed. The hoses have clamps.
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