Ok let me give a little bit of history before I jump into the problem. About a week ago I replaced a power steering pump on my buddie's 2005 F-250, it was showing symptoms of being bad by whining constantly and increased steering dificulty at lower RPMs. The truck has 140,000 so instead of doing the flush we opted to simply put in a new pump and then brand new fluid of course. Overall the install went well and the new pump worked good. The only thing that does still happen, is the brake pedal makes a whining noise every once in awhile while braking. It has been doing this since before the new power steering pump.

Now this week about 100 miles later, driving down the road his truck loses all power steering and his brakes become very stiff. Ok, now onto the diagnosing: the truck is not leaking power steering fluid on any of the hoses. The inlet line into the hydroboost is pumping fluid, and the outlet high pressure line from the hydroboost is confirmed to have fluid going through it. There was no fluid going through the low pressure return line on the hydroboost though, but I assumed that may be normal depending on the load and pressure of the system. I only got to look at the truck for about 30 minutes yesterday so that about as far as I got into it for diagnosing.

Any ideas from anyone? My generic thoughts are usually its the last thing thats been touched that would cause problems. So maybe the pump simply isnt building enough pressure.

 

When the brakes are pumped or the steering wheel turned you should have flow from the low press. return line. That is how I flushed my system.

 

I will jack the front end up to see if it makes a difference, but the wheels cannot turn very far on the ground, and the brake pedal is very stiff.