steering is difficult on 2001 BMW 540i

The steering on my 2001 540iA is acting up. It is somwhat harder to turn to the right, gradually getting easier as the car warms up. There is also a suspicious "whirring" sound--sort of like it wants more fluid. I'd like to do the KISS process and first check the fluid to see if its low---but I can't find the filler cap or the reservoir. Would appreciate advice on: (a) location of filler cap/reservoir, and (b)if low fluid doesn't cure the problem, what is/are the likely cause(s) of the steering problem?

by in Columbus, OH on February 11, 2011
1 answer 2 comments
ANSWER by on February 11, 2011
as you face the engine, the power steering reservoir will be near the front slightly to the right. it has a fluted screw-on cap 1.5" in diameter. on removal, you will see a small dipstick attached to it with level rings. add fluid to the mid-point not filled to the rim. the cap should have the type of fluid required; if it says CFS 11S, it is Pentosin and is not DexIII ATF. you must use the correct fluid. after that, if the problem persists, you need to have the steering checked by a qualified BMW specialty shop.
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COMMENT by on February 11, 2011
An excellent answer from Overbys. Zee
COMMENT by on February 11, 2011
After reading your incredibly quick reply, Overbys (and thank you very much), I checked the cap and found no markings other than "use ATF only" so I'll check the hoses, tighten/replace as needed, then fill with Dexron as you've described. Zee: thanks for the supporting comment as well.