I have a 91 560 SEL. My power steering pump is located
in the front right. It is mounted just in front of the drivers side head and cam cover.It has a 3" diameter black cap with a 3/4 " plastic thumb screw. This is where I add
power steering fluid. I add it often due to a line seeping which I need to replace soon.
I belive there is a full level indicator line in the reservoir but I usually just make certain the fluid covers the top of the filter tower.
The RED capped dip stick located at the left rear of the air cleaner on my car is the auto transmission fluid level indicator.