Recommended Brands for V-Belt & Powering Steering Pump
 

Hi fellow W164ers,
Appreciate anyone giving me an insight as to what brand to look for when searching for V belt and Power steering pump.
Thanks,

Gates for the belt.

Power steering pump is almost bullet proof unless the bearing goes. What is the problem?

First thing in the morning everything is fine. However, once the engine is warmed up after say 20 minutes or so, that's when steering becomes stiff at idle or very low speed unless you push on the gas then it becomes easier to steer, otherwise impossible. Hydraulic fluid is fine.
There's also a whining noise when steering at low speed. The whining is also heard at the start when the engine is cold.
Thanks,

A belt will not solve that. The bearing has failed.

What ML are you asking about?

Replace the belt but don't be so quick to replace the pump. The whining sound is usually attributed to air being trapped in the P/S system. When the whining starts, remove the cap and look into the reservoir and see if there are any bubbles in the fluid. If need be have someone turn the steering wheel back and forth while you check for bubbles. Don't mistake wavy fluid as bubbles. If you see bubbles, you must replace the reservoir and O-ring.

Also keep in mind that an ML500 has Speed Sensitive Steering which has an SPS Valve Y10, attached to the rack and pinion.

This valve controls the looseness or stiffness of the steering depending on the speed of the veh.

Great insight, I will look into it. However, how would you explain the stiff steering at low speed/during parking/idle when the engine is warmed up, not when it's cold. Is air an effect for this symptom.
How about the brands for v belt.
Thank you.

In post #2 I have already said that Gates belt should be bought.

As for the SPS valve, it could be getting stuck.

Just do the test of the P/S fluid check for bubbles.

Why did you check for bubble at 2k and 3k RPM? Repeat the test at idle as soon as the eng. is started.

Power Steering Test
 

Tested for bubbles at idle this morning when engine cold. Still no bubbles.
Please see the attached for the whining noise at the time.
I should add that while there is no apparent leak, I end up topping up the hydraulic oil around once a month, not much though.
Thanks

https://cimg3.ibsrv.net/gimg/www.mbw...2a51778dd5.jpg


Did you look into the reservoir while the wheel was turned?

That is not a bearing noise, it is a P/S noise/whine caused by air in the system. You probably have a small leak where the reservoir attaches to the pump because the O-ring has failed. Reservoir and seal must be replaced.

Before replacing anything, inspect the area of the pump and reservoir for fluid leak.

Then check the rack and pinion for leaks.

I still think it's the pump bearing. The symptoms sound classic to me.

You replace the pump.

You were absolutely correct. I removed the belt and checked the P/S pump pulley. It would turn smoothly with a slight push of a finger and very quietly too, no noise or screeching or any play in/out direction, as you would expect from a bad bearing. So for sure it's not the pump, at least it's not the bearing.
Then I removed the under cover to look at the rack and pinion. There I noticed everything was covered in oil, almost the entire left side (driver's) of everything under the pump were covered in oil, and the other side was completely dry.
I checked the low pressure hose, high pressure hose connections, no leak was found. where else would a pump be vulnerable to leak?
don't know whether they are the remains of the old leaks last year. I sprayed the area with brake cleaner and am going to drive the car to see if I still get the oily surfaces. Point is, as for the steering fluid, I lose very very little. I'm sure the extent of the splatter could not have been due to the p/s fluid leakage; we'll see later on.
So, what would you think would be the problem. I managed to reach the electrical connection to Y10, it was sound and firm. With the present feel of the steering, how do you think I can test Y10.
I do appreciate your input.
One more point of notice; I lifted the front wheels and starting turning lock to lock slowly; when I turned right, passenger side, slight movement on the fluid in the reservoir, more like a suction movement; then when I turned left, the fluid rose. like a push from under, and every second time, it even overflowed. This is with engine off and cool, and turning the wheels very slowly. Starting fluid level was under the lower neck of the reservoir.
Thanks

Dundee shoots. Dundee scores. Again. :popcorn:

https://cimg2.ibsrv.net/gimg/www.mbw...03d144affd.jpg
If the leak is at the head or one of the boots are leaking, you must get a rebuilt or used rack and pinion. The boots are only dust covers so don't think that replacing the boot will correct the leak.

Regardless of what rack you choose, replace the reservoir and O-ring at the same time. As previously informed, the bleeding must be done prior to starting the eng.

Why worry about this now. Remember that you still have to replace the rack and pinion.