I can't answer your question specifically but let me share a recent experience and give you a first step recommendation.
This past weekend I changed all the PS hoses and reservoir on my son's 2002 325XI. This included a full fluid flush.
- Working on the XI is a tight fit - I had to get at all the hose connections topside except for the lower suction line into the pump. A hose clamp replaced the factory BMW clamp.
- The LUK30 is a standard pump on all XI models I believe. You can look it up with your VIN on REALOEM
- I can't imagine the extra work to get the pump out on the XI. It was a tight fit just for the hoses and you may have to remove a sway bar, subframe or other extra parts to get the pump out.
One thing that may be happening to you is the filter in your reservoir is clogged causing starvation/cavitation when you turn the wheel. I recently was at an Indie BMW shop with my 2011 328i getting a "in between" oil change (still to new for me to work on and they only charge $79 for the oil change). Told him about my upcoming PS job on the XI and he told me to make sure to change the reservoir as there is a filter in there and they can get clogged up.
My recommendation to you as a first step is to change the reservoir and fully flush the fluid, don't use the Turkey Baster method. Here is how it worked for me thanks to a guy named STARLESS at BimmerForum - do a search he has some photos.
1. WIth the reservoir out - attach a Hopkins Measu-FUnnel to the suction line. You can buy the Measu Funnel at WalMart for $5. The hose fits right in to the suction line, just take off the little adapter and set it aside
2. Use the adapter to attach to the return line and then get 6-8' of 1/2" id x 5/8" od nylon hose (bought mine at Lowe's for .27/ft). Attach to the adapter and run the hose into a bucket - I use a home depot orange bucket for used oil and put the lid on ...just in case it came out really fast
3. Make sure the car is up on jack stands where you can turn the steering wheel freely.
4. Prime the funnel - make sure that the fluid runs all the way down so you have a solid column of fluid, with no air. This took me about 5 or 10 minutes. There is a little filter on the Measu Funnel and it slows the flow up initially.
5. I used Redline D4 ATF, there are plenty of choices for you to pick from. Overall the system took about ~2QTS plus some I threw away in the funnel and the return line. I started with 4 Qt's. Have about 1.25 QTs left
6. I had son number 1 start the car while son 2 held the funnel - note that I had a QT of fluid in the funnel already. I poured in the additional fluid as the first quart was consumed pretty fast.
7. I told my son to move the wheel from lock to lock - as soon as he moved the wheel the fluid jumped down about a 1/2QT very fast and then steady.
8. I saw the old fluid coming out - was disgusting, looked liked infected blood. There was quite a bit still in there even tho I had all the hoses off.
9. Kept going until the return line was solid bright red.
10. Shut the car off and disconnected the funnel and hose and installed the reservoir, ran a little and topped off again.
11. Overall worked great for me.
You should change your reservoir anyway. This is an affordable first step and may save you hours of time and money. I believe they are ~$50 at the BMW dealers and less online. This would be a good way to start and to flush your system of all the old fluid which is also highly recommended.
You will need some hose clamps to reattach a new reservoir so please get those ahead of time.
Last edited by VizslaDriver; 01-04-2013 at 10:00 PM.