I have a 2006 F250 super duty, recently the truck was involved in a collision. The damage was on the front driver side corner of the truck and the P/S reservoir was busted in the crash. After everything was repaired the brakes began locking up sometimes if I parked on an incline but would release if I turned the truck off and started it in neutral. Today I started the truck and the brakes locked up and would not release. I had to have the truck towed home. The brakes release as long as the engine isn't running, but as soon as you start it they lock down. If you turn the wheel you can watch the brake pedal pump up and down on it's own.

Could it have anything to do with the P/S reservoir having been replaced? Air in the hydraboost system maybe? Any suggestions or ideas greatly appreciated.

 

Hello The Shape and welcome to FTE.

What engine do you have?

 

Oh sorry it's a 6.0

 

Sounds to me that the pump is bad. every once in a while, you'll get a bad pump when replacing one. was it replaced with an OEM pump or auto store pump ? auto store pumps have a high failure rate.


did the replace the whole pump or just the reservoir ?

sounds like the pump is making back pressure when the motor is running.

 

Just the reservoir

 

It sounds like there are some parts of the broken reservoir that have gotten into the hydroboost actuator causing it to apply just like you had the brake pedal pushed. If this is the issue, then a new booster and flushing of the system may be all that is needed. However ......

I would get the insurance company involved and bring up the point that the system is malfunctioning. And even if they get this immediately repaired, your concern is if there are other particles in the system they might cause a repeat issue and apply the brakes unexpectedly while you are driving. Also bring up that if such a case happened while you were driving the brake lights on the vehicle would not come on as those are operated by the brake pedal switch. Would not be good to quickly slow down on the highway and the driver behind you not see any brake lights.

You might get everything in the power steering and brake system replaced, which if my premise is correct, is what is really needed.