94 Ford F250 brakes

[wanderingeye]

I recently bought a 94 Ford 7.3 diesel 250 with 70,000 miles on it in exc. cond. Upon changing the oil, the mechanic inspected the entire truck and determined that the front brake pads needed replacing, which we did. After the replacement, the brakes worked fine but the pedal was soft and would gradually go toward the floor. That seemed to indicate that the master cylinder was the problem. After replacing the master cylinder, I still have the problem. The mechanic is baffeled. Any suggestions?
Thanks, Tom

 

[bftank]

i would venture to say the brake lines have air in them still. you need to bleed the whole system until all you are getting is a steady stream squirting out of the bleeders. if it worked fine before it is not the master cylinder.

because you have air in the lines it will compress instead of pushing the fluid giving it a spongy feel. panic stops cause the brake pedal to go to the floor. i had this problem in my burb. couldn't make it up a steep hill tried to back down and only the fronts were grabbing. made for a scary decent. they worked ok intown though.

 

[wanderingeye]

F250 brakes

Thanks for the reply. Our situation seems to be outside the normal problems encountered with brakes. We bled the brakes 3 times, at the master cylinder and then at each wheel with the engine running. We put at least 1/2 gallon of break fluid through the system. The mechanics are very experienced with Ford trucks and tractors and big heavy vehicles. and are baffled by the problem. We have examined every brake cylinder and brake line, no pin hole leaks anywhere. We even bypassed the ABS system. If anyone has had a 1% experience, I would be interested in hearing about it. Thanks Tom

 

[Wyowanderer]

Thanks for the reply. Our situation seems to be outside the normal problems encountered with brakes. We bled the brakes 3 times, at the master cylinder and then at each wheel with the engine running. We put at least 1/2 gallon of break fluid through the system. The mechanics are very experienced with Ford trucks and tractors and big heavy vehicles. and are baffled by the problem. We have examined every brake cylinder and brake line, no pin hole leaks anywhere. We even bypassed the ABS system. If anyone has had a 1% experience, I would be interested in hearing about it. Thanks Tom

Tom,
have your mechanic take the disc pads off and verify that they're installed correctly. I know this seems like a strange thing to say, but a fellow on another site had a similar problem and traced it to incorrect pad installation.

If the pedal goes to the floor, you ought to have a brake fluid leak somewhere.

 

[toy_tek]

Did they try pressure bleeding in to the low side (caliper/wheel cylinder)? This process involves removing excess fluid from the M/C reservoir with a turkey baster. This is the best way to remove air as it forces all the fluid&air upward as opposed to downward as with standard brake bleeding.

Good luck.

 

[truck mechanic]

I see this all the time, replace the vacume pump. what happens is you hit the brake pedel, it uses up what little vacume is in the system, then as the pump builds vacume the booster starts to work and gives you that fading brake pedel feeling, trust me I ve fixed a lot of trucks others couldnt be cause they never thought low vacume.
Paul

 

[wanderingeye]

F250 Brakes

Thank you everyone. I will bring all of this up to my mechanic. We have checked the vacuume pump but it's worth rechecking. Thanks Again. Tom