W211 power steering strange noise

[ayadov77]

Hello everyone, and thanks in advance for helping me.

As you can see from the video, every time I turn the steering to the left or right, when it hits the end it makes a noise which is different from that famous whining noise that PS pump makes.
I tried to duplicate the noise by turning the wheel by hand. No noise. So I think its the pump.
Already checked the fluid, all good, the suspension links struts, springs all seem OK.
The noise happened very suddenly, I haven't replaced any parts previous to the noise.
The noise is less noticeable when driving.
Also steering wheel has vibration when turning.
Hope the vedio gives more details to the problem.

Now I showed the car to 2 independent mechanics, first said change the pump, second was pretty sure it's the steering rack.
I'm confused, and don't wanna spend hundreds of euros when not sure where the problem lies.

Any help / suggestions welcomed.


It's an E class S211 Estate from 2007.

 

[Uncle Benz]

I'll throw a third idea into the mix then! It sounds like the belt is chirping to me. This could be a worn belt, worn tensioner or seized alternator freewheel pulley (if it has one fitted). The engine sounds "throbby" to me, so I'd look at the alternator pulley first. Does the belt appear to be vibrating a lot when the engine idles?

 

[Arzaam]

sounds like the power steering bypass valve is noisy, have you checked for any play in the rack? unlikely to be the rack in my opinion. I would also check the auxiliary belt and all pulleys, saw one which made a similar noise at full lock and one the pulleys used to slip on the belt under load. I don't see it being that big a problem though unless it gets worse and if the assist is smooth and not jerky and there is no leaks or play in the rack. just avoid full lock when stationary.

Edit: Uncle Benz typed out first about the belt part.

 

[ayadov77]

Good morning Arzaam and Uncle Benz, thank you both for your help,
Today I replaced the v belt and pulley kit, the noise is still there,
I noticed no vibration with the belt or the rack, but when I touch the hydraulic line which comes from the pump it vibrates a little only when the noise happens.

Arzaam could you please tel where that PS bypass is.
Thanks again

 

[LostKiwi]

+1 for belt slippage.
You should never hold the steering on full lock for any length of time anyway but that definitely sounds like belt slip.

 

[Arzaam]

Good morning Arzaam and Uncle Benz, thank you both for your help,
Today I replaced the v belt and pulley kit, the noise is still there,
I noticed no vibration with the belt or the rack, but when I touch the hydraulic line which comes from the pump it vibrates a little only when the noise happens.

Arzaam could you please tel where that PS bypass is.
Thanks again

the pressure bypass valve is part of the control valve built into the pump, basically on full lock it can be noisy and its a different sort of noise then a power steering whine which is considered normal. the valve maybe stuck or not opening to purge pressure,
the hydraulic line also comes from it so the vibration you felt in the line maybe connected to it.

to verify this get a automotive stethoscope and put it on the pump and turn it to full lock and see if you can hear the noise from the pump clearly, otherwise use that stethoscope to see what makes that noise, you can even check the rack that way.

 

[ayadov77]

I decided to replace the pump because I think this is where the noise comes from, so I hope the new pump with new MB fluid solves the problem, I'm still not sure whether go for a new pump or 2nd hand, there are many used pumps online can be bought for around 100 euro, also there are new pumps from not very well known manufacturers like (RIDEX and STARK) for - /+ €120, other known brands are almost double the price.
I wonder if anyone used these brands? Am I looking for troubles by choosing the cheaper ones?
Also about the hydraulic flash, how much oil do I need for a proper flash?

Thank you Arzaam for the explanation, very clear.

 

[Arzaam]

welcome and I don't know about the brands as no personal experience with them but assuming you mean PS flush 2 liters should be enough to flush it, capacity is 0.9 litre I believe, heres a pdf that I think I got form a online forum somewhere but it illustrates the procedure if you want to do it yourself maybe it can be of some use.

 

[Arzaam]

though I personally would have driven with your original pump till it started getting louder or would have confirmed with a stethoscope to make sure I didn't replace a part that was not needing to be replaced but that decision is upto you hopefully you'll have all the info you need.

 

[ayadov77]

Ya, I thought about this too, problem is it's a Taxi, so every time I make sharp turn, I have to apologise to the passenger , it's very loud, and I can't stand the look from bypassing people.
I'm on my way to get one of those stethoscopes, fingers crossed.

 

[ayadov77]

Thanks for the PS FLUSHING PDF, downloaded and saved.

 

[Arzaam]

I see best of luck hopefully it'll be sorted soon!