Power Steering Moan Solved?...
 

Ok, so I posted here a long time ago about the hydraulic moaning sound I get in my 09 C63 in the morning. Happens on one of the first few turns to the right and usually not again until the next day (or maybe next week). Very loud and obvious. Even my 14 year old said "what was that?" Others here have said they've experienced the same thing. My PS fluid is full and not contaminated. Has anyone here actually figured out what this annyoning little glitch is and gotten it fixed? I do not like gremlins.

This EXACT same thing has just started happening in my 09 SL63, only when i turn to the right exiting garage in the morning etc etc. Would love to know what the hell it is. Car only has 17,000 km on it.

Totally unacceptable

Sounds to me like a pressure relief valve. Too much pressure building up when the fluid is cold or the steering is turned too far against the lock. They tend to vibrate a little as they bleed off pressure causing a moaning or groaning sound.

Might be able to shim it to stop it from happening.

had the same problem but mine only happened in the cold.
BUT since i changed my tires from the pzeros to the nt05's even in the cold it dont do it no more:nix:

Difference in side wall stiffness making the PZeros more resistant to turning?
This could build up higher pressures in the power steering system?

I don't know but I'm not going back to the Pzero's.

Bumping a 6 year old thread....

My car started recently making a slight moaning sound in the cold. Only when turning left. Almost sounds like a rubber on rubber type of sound. Any ideas?

with my W211 E63 I had my buddy drain and refill the fluid with new Mercedes power steering fluid. groan was gone...a year later and 10,000 miles later...groan is back, but only slightly.

I've got this too. Only happens when it's cold (which is 85% of the year here) but on hot summer days, it never does it.

After worrying about it at first and taking it to MB and another place for a second opinion, I just accepted it was a quirk of the car. My bushes and all steering/suspension components perfectly fine. I never was able to work it out.

There is a weak spot in the steering system. The reservoir has a small screen that filters fluid, it gets dirty and clogged with time/mileage. Sometimes, the fluid is new, the pump and rack are in excellent shape but the noise is from the cavitation in the pump.
Here's a thread with the dirty screen pics:
https://mbworld.org/forums/ml55-amg-ml63-amg-w163-w164/494969-power-steering-pump-fail.html#post6875441

Keep in mind, all M156 engines share the same steering reservoir.

hey brutha,
Kind of off topic but how do you like your tune?

^This. I had a similar noise and replaced the reservoir and the fluid and the sound disappeared. I'm guessing I had dirty fluid and a clogged screen. FCP Euro offers a kit including an MB-braded reservoir and the fluid for a very reasonable price. The reservoir is right at the top front of the motor and replacement took me an hour or so plus about 30min to bleed the old fluid out.