Check the fluid level in the reservoir - a common fault on ML's is a leaking pump & mine was replaced under warranty. Coincidentally mine made no noise as an indicator of failure.

 

thanks bob- fliud level looks fine- assist just goes away when hot- i wonder if having the fluid flushed might help- maybe it has been contaminated somehow by moisture and is failing when reaching high temps?

it almost seems like a hose is being blocked or maybe a valve is sticking. does the ML have a steering adjustment where at high speeds it changes ratio?

im just throwing out ideas... no leaks, no whine and it works fine until hot-

 

TBH my leak was very obvious, so it doesn't look as if that's your problem.

Might be time for a dealer or independent to look at it.

 

You might have air trapped in the lines and they need to be bled.
It' funny that there is no groan when it malfunctions

 

off topic- Zak i see you live in Bernardsville, beautiful on that side of Jersey- I used to live off Larger Cross road right off of Lamington in Bedminster..

 

I had that same problem with my 2007................Pump had to be changed.

 

yea i figured as much... im just going to keep driving it till it gets worse- its fine at speed just heavy at very low speeds after the car gets hot-

 

If you have air in the lines and/or wish to bleed it, turn it on and turn your wheel lock to lock a couple of times. This will bleed any air from the lines. Worked like a charm on my SLK.

 

did you remove the reservoir cap while performing this?

 

True............4 or 5 complete cycles are better. But lift the front end off the tires to avoid wear on the tires and strain on the steering mechanism.

 

No.........The cap allows the small amount of air to escape without carrying fluid with it. Air got into the system when they changed the pump.

 

I have the same problem. Any resolution?

Hi Gisham,

I have the same problem with my ML500 '06 after changing my fluid. No pump noise. Heavy/non-assisted only when hot. Pump not "relieving" initially on on hitting stop - this would suggest air in rack and therefore no pressure initially on stop as air compresses. When front wheels in the air, engine off and turning lock to lock some air/fluid noise can be heard.

I don't believe air entered the system on flushing as I vacuumed the pump, removed the return line at the reservoir and blocked the return hole, had the end of the return line under fluid in a container, filled the reservoir, turned lock to lock with engine off until return fluid ran clear while over topping reservoir fluid (2 man job). Then connected hose again. Nice clear clean flush using about 2 litres of fluid total.

System was perfect before flush but there was weeping from the return line and it needed a trim and hose clamp (rather than MB clip) so I chose to replace the fluid as I needed to drain the reservoir for the fix.
Steering was perfect initially after change and with my test drive but my wife drives the car and not until it got hot did the steering "fail".

Did you discover the root cause of your steering when hot issue?

With thanks in advance,
Russ...

 

i had 2010 300cdi ml , just wondering how long is the warranty at power steering pump, as my steering its getting heavy when the car goes hot? anyone can help

 

mr ALV

hi mate i just have the same problem with my 300cdi 2010 as well i rang mercedes and they said its 3 years warranty that mean well, i've just try feel thing as my car just getting heavy after about 1hour drive i took to some guy and been told was the proportion valve, well the change and still the same now i took back to then they said it normal, so if its normal heavy they should give my money back as they didn't fix the problem, after reading many forum, im just wondering if only happens when the car its hot , that mean the fluid its hot and stop goes running at power steering .... or could be speed sensor after the wheel getting hot stop working and make the steering heavy . the only thing which i don't believer its the power pump as our car the pump its electric . its complicate as the car doesn't show any fault at all.. but i will try sensor first its cheaper...if you have any lucky please let us now mate,

 

ML55's W163 and ML500's W164 are equipped with what is called, Speed Sensitive Steering which allows easy steering at parking and low speeds, but stiffer steering at higher speeds.

This feature is controlled by the Y10 SPS Valve, attached at the rear of the Rack & Pinion. This valve is replaceable.

Do not indiscriminately replace your P/S Pump or your Rack & Pinion without considering this possibility.

 

did someone solved this problem.. i to have the same probleme...I think it's the sensor rack...

pleas helppp

 

I have the same problem on my ML 500 2006, I found out thou that the power steering comes back when I increase the RPM >1000 (I shift to neutral or park while parking). Not sure if this info provide some help.

 

Did anyone resolve this issue?

 

Everyone asks questions but never indicate what veh. they are referring to.

If it's the W163, you are on the wrong forum

If it's a W164, Please UPDATE YOUR PROFILE in USER CP.

 

Resolved reply: Mine got worst over two weeks. A new steering pump and all good for 2+ years.

 

Resolved reply: Same symptoms. Works cold, fades hot. Mine got worse over two weeks until almost no assistance (actually felt like it was fighting back). Replaced pump and no problems for 2+ years.

 

Thank you RussMc. Did you use a OEM mercedes pump or something else? I am contemplating a rock-auto pump or a cheaper amazon pump. We'll probably only have the ML another 2-3 years if that long.

 

I bought a cheap pump for my ML430 and it turned out to be a complete waste of money. As soon as it got hot the pump no longer produced enough pressure. The trouble was, I thought that my problem must be something other than the pump, because obviously I had just changed it. Only when I finally came to the conclusion that it had to be a problem with my new pump, did I buy and install a genuine OEM pump and it's been fine since.