I just happened to be searching for a way to diagnose my power steering problems correctly

1: I don't have any power steering at low engine speeds.

2: The power steering works perfectly when the car is cold, the hotter it gets the worse it gets.

3: I would say that it's choppy. Meaning, even when the car is hot and the power staring isn't helping me, it does sometimes still assist me some what in turning the wheel.

4:The steering wheel seems to be a bit loose.

I’m thinking a new Power Steering Pump. I replaced the PS fluid reservoir last year due to a leak and noise. I currently have 165,000miles.

__________________
Russell McMahon
Tulsa, OK
2001 CLK 320
1992 400se
1993 400e
2000 320ML

What fluid are you using?
I would try flushing & using fresh fluid in another new reservoir.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator

I had a similar problem where an antifreeze coolant leak was dripping on the belt causing the power steering pulley to slip. It took me forever to find! The steering was fine sometimes, "jumpy" when hot. Just a thought.

__________________
John
2001 ML 320
1988 560 SL
2009 Toyota Tundra TRD
1992 400 E (sold '07) (bought back, '13)
2008 ML 350