W211 steering problem

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selphy

Active Member
Joined
Mar 10, 2013
Messages
96
Car
Mercedes E220CDi
My 2008 E220Cdi (70K miles) steering is heavy at all speeds and I think it's getting worse. When I drive other cars I really notice the difference now. Recent checks and service history:
  • Check tyres (fairly new) and tyre pressures. Tried over-inflating but it has no noticeable effect on steering.
  • New bottom balljoints on both sides (genuine parts fitted).
  • 4 wheel alignment including installation of camber bolts.
  • Power steering fluid level OK (CHF11S).
  • Serpentine belt, tensioner and idlers replaced.
  • Replaced PS fluid (sucked it out and refilled reservoir several times over a few weeks). Old fluid was a little grey and slightly smellier than the new stuff but it wasn't too bad.
  • I tried jacking up the front of the car and the steering doesn't feel heavy but neither is it superlight even with front wheels in the air. There is no strange noise or roughness anywhere.
  • I disconnected the track rod ends and checked the hubs can be swivelled freely. They seem OK, fairly easy to swivel by hand until they are approaching full lock- then you can see various rubber bushes in the suspension arms starting to deform slightly. I presume this is to be expected.
  • With the track rod ends disconnected the steering feels heavy to turn without the engine running - I presume this is also normal because fluid is being pushed around in the rack? I didn't try turning the steering wheel with the engine running because I didn't know if I could damage something by doing so as there would effectively be no end-stops and I didn't want the tie rods clanking agains the backplates etc.
Any suggestions on what to do next?

I'd quite like to check the pressure from the pump but I don't have the right hydraulic fittings to rig up a gauge. I've read that a failing PS pump would be worse at lower engine but I can't notice any difference in steering feel if drop down into a low gear to get the engine speed up high so I doubt the problem is with the pump.

Could there be some joint in the suspension that only gets tight when the weight of the car is on it, and how do I troubleshoot that?

My car doesn't have speed sensitive / parameter steering so I don't think there is anything that needs resetting or re-coding.

Thanks!
 
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