[Darkmann]

MY05 500: Mine has started. I really don't understand why, becasue truck sits in garage most of the time, and is driven probably 4 -5 times a year, usually from MD down to SC, LA or FL. I did notice a couple of drops of fluid on the garage floor, traced it to the PS hose that goes into the reservoir at the top. The clamp screw was quite lose, so I tightened cleaned and just watching for now. I also have been following http://www.benzworld.org/forums/w163-m-class/1791050-dont-understand-ps-whinning-advice.html and am wondering if I have cavitation due to bad reservoir. I will have the reservoir replaced but would like to have opinions first. Thanks.

 

[edcarls]

Replacing the PS fluid reservoir resolved mine.

 

[43sqd]

If the hose was loose and leaking even a small about, it will suck air into the system.

You didn't say if tightening the hose resolved the noise, but if it didn't try the bleed procedure. If that doesn't work then you will need a new reservoir and after replacement, DO NOT START THE VEH and then bleed the system.

 

[Darkmann]

If the hose was loose and leaking even a small about, it will suck air into the system.

You didn't say if tightening the hose resolved the noise, but if it didn't try the bleed procedure. If that doesn't work then you will need a new reservoir and after replacement, DO NOT START THE VEH and then bleed the system.

Thanks Squid. That was done a couple days ago but I was not expecting it to solve the problem and it did not. My plan was to monitor leak and then bleed following the proc you provided in the link I referenced. I took truck on a 3Hr "steering torture" drive and now I am just monitoring for leaks while checking out prices for PS reservoir. The last time I had this whine, the truck was under warranty and MB's solution was to replace the entire steering rack! Thanks man, I really do appreciate your help.

 

[Shockage]

I would also check power steering fluid. I had the reservoir and the pump replaced for leaking power steering and they developed whine again.

For me the solution was to pour extra power steering fluid in beyond the Max mark at room temperature. Even on the old pump and reservoir that was leaking, I noticed every time I "overfilled" the reservoir by a few milliliters, the whine disappeared and the steering was more responsive at idle. The same for my new pump.

If I am not mistaken this is a common problem and just topping the fluid off a few millimeters over the max mark should do the trick.

Can someone verify my anecdotal advice such that I am not recommending something problematic?

 

[Darkmann]

UPDATE Yesterday I had to take a 2.5 Hr trip to DC and decided to take the truck. I also decided to have the fluid topped off at my local MB shop just to be on the safe side. I noticed a couple of things - first, starting and driving to the shop (~ 8 miles away), I could not hear any discernible whine. Whatever I did the previous day, seemed to have worked a bit. Second, at the shop, they topped off but pointed out that the whine was still there. They were right, it was there but certainly extremely faint. Again, that is good news in the sense that the leak was the cause of the problem. They did also point out that the screen could have been damaged as 43sqd showed. The plan now is to first bleed and then replace the reservoir if noise is still there. I may just put in a tad more than max like you suggest.

By the way, if the screen breaks, doesn't that cause debris in the entire line?

 

[art_arev]

After replacing the reservoir flush your PS fluid. The debris will come out.

 

[Darkmann]

After replacing the reservoir flush your PS fluid. The debris will come out.

Thanks.