My son bought a 2006 ML500 with steering issues, and if I had hair I’d be pulling it out trying to fix it. The previous owner said that the power steering pump had just been replaced but it certainly doesn’t look new. The steering is hard, worse than my old pre-power steering cars. We swapped reservoirs and put in a new power steering pump yesterday. We bled the system by turning stop to stop for about 10 minutes, topped off the fluid, and set it down off the jack. After about 10 seconds at idle there is now a serious grinding sound and the wheels are almost impossible to turn. What have I done, and what can I do? Help!

 

See fault codes. Servotronic valve may be broken.

In my car, I changed the servo pump 3 times, the steering rack 1 time, the steering valve 1 time. not as soft as the first day. but not as stiff as hydraulics.

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When you bled the system, was the engine running? MB recommends that the engine isnt running when you bleed it. Is the grinding noise only when you attempt to move the wheels, or always?

Regarding the stiffness of the steering, also look at the universal joint/knuckle at the end of the steering column. These are known the seize up as happended to mine. Sometimes they only impact part of the turn of the steering wheel, but evetually impact all 360 degrees. This is often overlooked with steering issues. Its not a difficult fix. Good luck