steering starts to shake

[parasound]

My friend has a 96 explorer 4x4 and he started to get some trouble with the steering, when he turns, eiter sideways it starts to shake an wobble alot for a while. He also put it on a jackstand and turned the steering wheel and he could se both tires turning back and forth, at least 4 inches each way, and he had to physically stop the wheels with his foot, then they stopped wobbeling.
Anyone have any idea what this might be? Pump? Rack?
Thanks
Torbjorn

 

[MustangP51]

I had something like that happen before, I replaced the serpentine belt, it went away.

 

[parasound]

how could the serpentine belt cause this? The truck does this even when he's out of the truck and not touching the steering wheel, he checked the hoses from the pump, and he could not feel anything on the pressure hose, but on the return hose he could feel the pulsating oil
THanks
Torbjorn

 

[my98nnj]

He also put it on a jackstand and turned the steering wheel

Did he turn the wheels when the engine was off?

If that is the case then his power steering system has air in it and needs to be blead. With the truck on the ground, engine running, turn the steering back and forth, lock to lock several times. This will remove any trapped air and give him back stability in the steering system.

 

[parasound]

No, the engine was still running, and he tried to turn it back and forth, he also changed the steering fluid.
This wobble comes when hes driving and he comes to a curve, the whole truck start to shake. could it be any valves in the rack thats causing this?

 

[chapsdeva]

My guess is air in the steering. Explorers are know to get this if the wheel is turned while they are not running. This happened to me after I had to push my truck out of the driveway after the battery died. The steering shook bad while driving when I turned the wheel. I bled the system and the problem went away.

 

[JOEZ33]

Same here, I had turned the steering wheel one time with the truck not running. Then next time I tried to drive, the steering wheel and whole truck shook violently if I attempt to turn the steering wheel. I asked a friend and he immediately said to me "you turned that steering wheel with the truck not running didn't you?". It's a known occurance with the ford trucks. Try turning it lock to lock very slowly several times, then wait a few hours.... yes hours, and do again. On my truck this happened several times, and each time it took me two days to get it steering normal again...... whenever the steering shook, I could look at the fluid and see that it was all foaming and full of air bubbles.