PS Issue on 2001 4.4l X5

[pwvarley]

Hey everyone, I have searched various threads trying to diagnose my current problem without having to start a new thread but I have failed. SO I am coming to you all!

I am experiencing periodic tough steering. Usually at slower speeds the power steering seems to not work as well, but at higher speeds does not seem to be an issue at all.

In some threads I read that using white lithium grease on the U joint for the steering rack helps as it rusts over time, examining that joint I can see remnants of previous grease but looks rather old.

With the power steering reservoir cap removed, car turned on in park, moving the steering wheel from left to right causes the fluid to swirl around in the reservoir which to me makes me thing the pump is working.

Fluid is definitely extremely dirty and in need of being changed but could dirty fluid cause these symptoms?

And also on that note, when topped off how full should the reservoir be?

Any help is greatly appreciated,
Cheers