The whine is usually from cavitation because air is being drawn in somewhere. Clean and tighten the hose connections and then wipe the hoses clean and see if they start "weeping", if so, replace them, if fluid can "weep" out, air can be drawn in.
Next, clean and flush the hydraulic system and change the hydraulic filter in the reservoir, but first you must identify the correct filter as there are two types of reservoir. Go here and enter your VIN or car information:
http://www.realoem.com/bmw/select.do?vi ... E24&arch=1
(Look under "32 Steering- 32 20 Lubrication system")
to tell which one you have from looking at the type of cover and knob on the reservoir. Click on the one that represents yours and it will give you a diagram showing how it all goes together and a parts list.
The seemingly most common number is 32 41 1 128 167
($15 at
https://www.autohausaz.com)
The other number is 32 41 1 128 919 ($23 also at Autohausaz)
Discharge the accumulator by pumping the brakes 20/30 times, until the level stops rising. Remove the top "C"clip and screen. Get a turkey baster to empty the reservoir. Remove the remaining"C"clips, spring, cap and filter and clean the reservoir (the two I've done have had a gray film coating everything, let us know if yours does too).
Install the new filter, filter cap, spring and "C"clip. Fill the reservoir and run the engine. Go through the steps of discharging the accumulator, emptying the reservoir, refilling and running the engine 2 or 3 more times to flush out the old fluid in the lines, steering box, pump and regulator. To bleed the system, turn the steering wheel lock to lock 4 or 5 times with the engine running. Reinstall the top screen and it's 2 "C"clips. Don't forget to discharge the accumulator (pump the brakes) before you top up the reservoir to 3/8"(10mm) from the top. If you don't the system will be over filled. I used about 3.5 quarts of ATF to do all of this.
_____________
<img src="
http://bigcoupe.com/ims/pic.php?u=21GvpX2&i=228">
