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CRIS

CRIS 6/5/2011

1988 Chevrolet K1500 Silverado 8 Cyl 5.00L

Brakes

spongy brakes tried everything HELP

replace front left caliper, rear wheel cylinder on left side, master cylinder, proportion valve cleaned out the lines and bled system brakes hold good but i start the truck and the pedal goes to the floor the rear breaks catch air over night

3 Answers


Jimm

Jimm 6/5/2011

Have you performed a bench bleed for the master cylinder before installing? If not, this is a good place to start - check the 'How-To-Guides' for a detailed step-by-step instruction for the master cylinder bench bleeding. Check also the individual wheel cylinders and make sure the bleeder screw can be closed off - sometimes corrosion or dirt will prevent the bleeder screws from fully closing.

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mastec1970

mastec1970 6/5/2011

This is a fairly common problem: The isolation dump valve is leaking internally. The isolation dump valve is located below the master cylinder in the line to the rear brakes. It has a four wire harness. Disconnect the brake lines from the valve. Using adapters, connect the two brake lines together, and bleed the brakes. If the brake pedal is now normal, replace the isolation dump valve.

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mopar

mopar 6/5/2011

check brake booster and or check valve.

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