Is your Power Steering reservoir is 'sweaty' with oil? If so, try replacing the cap-seal. It's an easy / cheap DYI that solved a problem common to every BMW I've owned.

A simple fix for these get very flat. no more leaks

2003 530i No issues. Fits and functions. Stops that wet power steering reservoir

I had a small amount of oil leaking from my power steering cap. The cap looked great but i knew the gasket must have been worn. It solved my problem and i no longer have any oil or vapor escape.

Easy install goes between Power Steering Cap and Reservoir, just make sure your old one isn't stuck or hidden/flat on the cap.

This seal is easy to leak

I have an N54 motor and this seal fit perfectly for my stock power steering system. Had a small leak coming from the cap when driving hard and I haven’t noticed any leaking in the ~month since install.

I was getting the very common residue on the P/S cap, and took the occasion finally to switch out the o-ring. It worked perfectly. I still get just a tiny bit of vapor out of the vent hole, but the days of my entire cap being soaked with fluid are now over.

Fixed my problem with Power Steering Fluid seeping out over time. Always clean and dry now. Perfect fit and cheap solution.

Put this on a cap and have not had any weeping fluid since!