Date registered: Jul 2006
Vehicle: 1999 E55, 2001 E320, 1990 560 SEC, 2004 ML350, 2001 ML55, 1995 S500, 1998 SL500, 2010 E550 Sport zoo
Location: NW Arkansas, La Jolla CA, Hong Kong
Best to pop up front of engine cover..
To "fill" the power steering reservoir, best to "pop-up" the front of the plastic engine cover - turn reservoir cap counterclockwise approx 1/4 turn to release point - a small flashlight comes in handy sometime to check the fluid level - and use a funnel or "plastic turkey baster" to add fluid to top-off the reservoir to fill point.
It is highly recommended to use MB power steering oil - roughly dealer list USD$9 a quart.
When tightening the cap back onto the reservoir, turn clockwise, and make sure you tigheten firmly all the way to the full stop/closed position, which sometimes takes a touch more umph than you might think.
Push the front of the engine cover back down to lock it in, and you are good to go.