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Ask Keith Wayne Your Own Question
Keith Wayne
Keith Wayne, ASE Certified Technician
Category: Ford
Satisfied Customers: 131
Experience:  16 years in Field. Ford Engine Master, Chassis Master, and Diesel Specialist
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Ford f-450 dump brakes wont build up pressure, I have bled them and still nothing,

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Submitted: 7 years ago.
Category: Ford
Expert:  Keith Wayne replied 7 years ago.
Tim, Thanks for your question on Just Answer. What year is your F-450? Thanks Keith
Customer: replied 7 years ago.
2000 f-450 dual wheel dump truck. I did a rear brake job rotors, calipers and pads, now i bled the brakes and no air comes out but it wont pressureize thr pedal is still spongie, if i pump it up whan i am driving i have some presse but goes away. Thanks for your help.
Expert:  Keith Wayne replied 7 years ago.
Thanks, XXXXX XXXXX possible causes here. The most likely would be a failed master cylinder, a lot of time what happens is when you do a brake repair like a caliper replacement. When we bleed the brakes the brake pedal goes to the floor past where the master cylinder has been traveling and it damages the rubber seals inside. To test remove the brake lines from the master cylinder. plug the holes and when you push on the brake pedal it should be firm, and hold position, and should not fade. if it does replace the master cylinder and bleed the brake system. The only other component that may fail would be the ABS module, a isolation valve could be stuck open, to verify this you can bypass the valve with brake lines to restore your pedal. Thanks in advance for your ACCEPT. If i can help further in this diagnosis please let me know. Keith