Help Needed brakes locking up

[donmichalak]

My brakes will lock up-not solid but just enough to slow me down- while driving and then after a while release. When they release there is a clunking sound (just audible) coming from under the dash near the brake pedal. I am not sure if the problem lies with the master cylinder or the hydroboost or both. I have read a thread on another site with a similar problem and he just flushed out the power steering pump and replaced the fluid with new power steering fluid. My truck is a 1999 (july 98 build) F250 superduty with 7.3 diesel. I am looking for some advice or direction from somebody who may have come across this problem. Thank you in advance for any help .
Don

 

[JLDickmon]

I'd almost have to say neither..
I'd be looking more for a faulty brake flex hose..
next time it does it, crack the bleeder screws.. if it releases, your problem is in the hoses.

 

[dachshund]

If it were a hose, would it not pull to one side?

 

[donmichalak]

At first I thought it was my parking brake dragging but I checked them and they are OK. Once when this happened I was almost home so I coasted into my driveway and the truck stopped rolling when I pushed the clutch in. I checked all 4 wheels and they were all hot. The brake pedal is hard at the top when this happens as if I was already braking hard. That is why I thought it may have something to do with the master cylinder. I will keep you informed with what I find.

 

[dachshund]

Is your pedal staying down a little? Try pulling up on the brake pedal when it happens.

 

[JLDickmon]

At first I thought it was my parking brake dragging but I checked them and they are OK. Once when this happened I was almost home so I coasted into my driveway and the truck stopped rolling when I pushed the clutch in. I checked all 4 wheels and they were all hot. The brake pedal is hard at the top when this happens as if I was already braking hard. That is why I thought it may have something to do with the master cylinder. I will keep you informed with what I find.

well, it might...
high hard pedal is caused by fluid pressurizing the lines backwards from the calipers...

 

[bigrigr]

Could also be something to do with the hydroboost as well, evey time i've stepped on a brake pedal with no power assist(when it should have it) the pedal is hard as a rock. I'd say you need to check the hoses as stated above, the inner lining can "peel" off and block the fluid from returning to the master cylinder, thus keeping the pressure on the caliper and dragging the brakes, by opening the bleeder, you effectively release the pressure and the wheel should spin freely, it the hoses check out, then flush the power steering fluid in the hopes that you MIGHT flush out some piece of trash that is floating around in there. If that does'nt work then consider having the hydroboost/ps pump replaced

 

[arizona]

How would one go about a power steering flush? I experience the same problems.

 

[JLDickmon]

How would one go about a power steering flush? I experience the same problems.

Pull the return line at the pump (the one with the spring clamp on it) and point it into a bucket. Make a stopper out a bolt & a short chunk of hose for the stub.

Get three or four quarts of power steering fluid and a helper, have the helper fire it up and wobble the wheel 1/4 turn each way... keep fluid in the pump as it runs through the system. Shut it off when it runs clear, put it back together.

Fire it back up and turn the wheel lock to lock several times to purge trapped air. Drive it around the block, recheck the level, Boom-done.

 

[arizona]

Thanks. I hope this clears up my steering problems. I'm past due for new fluid anyways.