I noticed a rather strange issue with wife's 2007 GL450 steering a couple of days ago and hoping that someone might share some insight.

The steering feels very tight and heavy when the car is idling or pulling into a parking spot at low speeds. One the car picks up speed, steering goes back to normal (or at least doesn't feel as heavy). There is no screeching noise coming from under the hood when I turn the steering wheel from side to side. I've checked the power steering fluid and it was a bit on the low side. I topped it off but it didn't remedy the problem. I don't see any leaks on the garage floor and looking around the engine didn't notice anything leaking from the power steering reservoir (the reservoir was replaced just a couple of years ago as it had a bit of a leak).

Any suggestions?

Thank you in advance!

 

Tire Pressure?

I run mine a bit high (35 PSI Front), as I like the firmer ride and lighter steering.

 

MB500 - did you ever resolve this problem? I am now seeing similar symptoms and am curious to know what you did.


Thanks!

 

Check your tires. If you see wear or some cords on the interior side, that could be the problem and need to be changed. If not, check the alignment.

Feel free to go to the GL550 tire wear thread post where I posted a response about my tire being ripped along with the alignment being gone on my 550.

 

You have speed sensitive steering. It is very likely that the hydraulic valve on the steering rack is failing. They do fail. The valve needs to be activated via das and steering weight change observed accordingly.

Once diagnosed it is an easy fix.

 

I find that variable assist steering is not that easy. Since transmission/engine ECU, the trip computer, the ABS and Stability Control Systems - and some other systems - all are interlocked, I would first assess the speed sensor~$120. Lack of signal from the sensor makes a default open solenoid, giving a P050x or P0720 code. Your ABS/Stability control would light up.
If there is a DTC C1501, then check the SPS solenoid valve ~$260. A solenoid stuck at open would allow more fluid to pass making the steering light. At highway speeds, the car would have a jumpy-steering feel. A closed solenoid would be a heavy feel, especially at low speeds. If the valve is working, then check the PS pump~$250. A failed pump also gives a heavy feel with a P055x code. Lastly, the ECU~$$$$. You need DAS to query the ECU.

http://mercedes-bulgaria.com/Downloa...20Steering.pdf

 

it is usually that easy. all of the other culprits you mentioned will throw codes or light the dash.

besides, it is usually the steering rack solenoid.