B200 Power Steering Failing - Need more understanding

[praevidium]

Greeting from this side of the Atlantic!

My B200 electric power steering has recently started to making noise: a difficult-to-describe rattling/gurgling/grating sound that kind of reminds me of a rapidly flapping solenoid switch. It's intermittent and fluctuates in length from .5-2 seconds. The other day, the sound began to be accompanied by a twitch in the steering wheel when the car is stopped.

I'm thinking that maybe it's the ESP motor clutch (if there is such a thing on this car). Can anyone who has experienced anything similar offer some wisdom? I have a line on a replacement motor/controller but I don't want to start throwing parts at this without a little more knowledge.

 

[praevidium]

Checked today: no fault codes. I was hoping for something to nail down a diagnosis, but no such luck. I'm wondering if the mechanical side might be a secondary symptom and if the EPS torque sensor is the actual culprit.

Anyone?

 

[roheel]

I had the same issue with my B200 turbo. I was lucky to have the Mercedes tier 1 warranty which covered the repair. But I had to jump through hoops to prove to Mercedes it was a fault. I took several videos and even a technician on a drive with me after which they agreed. It felt like the car was possessed when you are at a standstill and the steering wheel moves itself.

Also it seemed the steering was always in low speed mode as it was way way too light driving at speed to a point where it felt unsafe.

 

[praevidium]

Thanks for the reply. Do you know what exactly they did to resolve the issue? I'm 'way past warranty, so I'm on my own and I'm loathe to go to the dealership (or even a third party shop) without having as much information as I can possibly glean.

 

[roheel]

They replaced the whole steering rack. I was told its a sealed unit with the motor and rack. I'm sure you can get it reconditioned. It's the motor at fault but you can't get that separately.

 

[praevidium]

So just to confirm, they said it was the motor and not a sensor that was at fault? That'd be good news for me since here I can get a discrete motor/control unit that bolts onto the rack. The sensors (or at least one of them) are built into the rack. At least, so says my copy of the MB WIS.

 

[roheel]

Yes they said it was the motor unit

 

[praevidium]

Alright. Thanks for the good information!