Brake problems. - Ford Powerstroke Diesel Forum
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Old 06-24-2014, 01:52 PM Rookie

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Brake problems.

I have scoured this forum as well as many other Powerstroke forums and have read many similar problems to mine.

Right now the brakes are hard when the rig is off but immediately creep to the floor when the engine starts and wont return on their own. The brakes work but you have to manually put your foot under the pedal and lift it up to release them.

Before we go any further....

Lets start with a brief history. I was hand me downed a 94.5 powerstroke F250 4x4 from my old man. It sat for a year or two and didn't run. He lives at the coast so of course the entire underbody is now a rust garden.

I threw a new starter (old one had corroded nearly solid), charged the batteries, put some sea foam in the fuel, cleaned the fuel bowl, changed the fuel filter and it fired right up.

A couple brake lines had rusted through, so I bent some new lines and bled the system. RABS, RR,RL,FR,FL.... then the master cylinder to be sure no air was trapped in it and I repeated the bleeding process again in the same order.

This did not improve the condition of the pedal. Again, brake pedal is hard when the motor is off, once the motor starts the pedal sucks to the floor(I wouldn't call it creeping because of how fast it happens) and the the pedal wont return until the engine stops running, then it slowly returns incrementally.

While the pedal returns with the engine off you can hear a knocking in the brake booster with every incremental return of the pedal.

I have plugged both ports on the master cylinder and the condition remains the same. So the problem can't be down stream from the master cylinder.

I am leaning towards a bad brake booster that has sh-t sticking or hanging up somehow. Possible internal corrosion from sitting for so long.

I don't believe it to be the vaccuum pump because if that were out the pedal would be hard with the engine running.

I am on severely limited funds right now. A new master cylinder costs $40 and the zero-loss brake booster is $170.

Is it worth spending the $40 to see if the MCis the culprit or should I just go ahead and go with the zero- loss brake booster first, since that is likely where the failure is occurring?

Please help me if you have ran into a similar problem. I know that many have on the OBS Powerstrokes.


Last edited by ClassyUSA; 06-24-2014 at 02:06 PM.
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Old 06-24-2014, 01:56 PM Rookie

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P.s. The ABS light comes on a couple seconds after the engine is running( I forgot to check to see if it was on when I plugged the master cylinder ports or not). And the parking brake light comes on and off randomly whether it is engaged or not.
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Old 06-24-2014, 06:19 PM
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On my 94, the symptoms weren't so drastic. The pedal would suck down and not return as fast as it should (it would return though). You get used to the feeling of it following your foot through the motions, but it would just lag a bit and felt funny. I replaced the booster with the zero loss unit and it fixed my problem. Back then it was only about $100. Cheers!
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Old 06-25-2014, 01:13 PM Rookie

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Last night I tightened the bolts that bolt the MC to the booster because my buddy thought he could hear air leaking at the connection. So after they were tightened(I got about a half turn out of both sides) we re-bled the entire system again.

The pedal was acting more firm but it would still eventually creep to the floor and would hang up and not return.


This morning I went out to fire up the beast and it had a really firm pedal after starting it. The pedal started to creep slowly so I pulled it back and noticed it didn't hang up at all. I then proceeded to pump the brakes about a hundred times really quickly.

The creep stopped and I have a normal brake pedal.

It returns fine and doesn't creep.

There must have been some last bit of air in the system (likely the MC) that needed to get worked out.

Anyways. Problem solved for now.

Hopefully this helps someone in the future.
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