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2001 ML320 & 2003 SL500
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Discussion Starter #1
Here Goes..
My power steering was making a lot of noise and leaking fluid. So, I went to my local mechanic and he told me that I need to change my reservoir. I had him change the reservoir with Mercedes P/S fluid
and it stopped the power steering fluid from leaking, but the groaning noise is still there.

I went back to my mechanic and he told me to change the pump in order to stop the noise. I bought a rebuilt A1-Cardone Power Steering Pump online and had it installed. Guess What? Groaning noise a little less, but still there.
After searching the posts here I went and tried to bleed the system myself.

1 – I sucked out the P/S fluid using a turkey baster and replace with a little Mercedes Benz P/S fluid.
2- jacked the 2 front wheels off the ground and put the key in position one ( I did not start the truck). Went back and fourth 50 times.
3- Put the truck back on the ground and checked the P/S level and filled to right level.
4 – I started the truck and turned the wheel and groaning still there. I even drove the truck for 50 miles and still groaning when turning the wheel while in park and driving at low speeds.

I went back to my mechanic and he told me that I should replace the P/S pump with a New and not rebuilt pump from Mercedes and that will stop the groaning. He told me that almost all after mkt P/S pumps make a little noise.

This making me nuts????
Question.
What is the make of the original Mercedes Benz Power Steering Pump. I am really trying not to drop $507.00 on a pump from the dealer.

Is my Machine giving me good advise about changing the new rebuilt pump that is installed??
I just want the power steering noise to go away.
 

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ML320 2002
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1,602 Posts
You needed to replace the reservoir instead of the ps pump. You should still replace it first before the second pump. If your mechanic did not bleed the system properly, the brand new reservoir will continue to make that noise because the diaphragm inside will be blown. Once it is blown, replacing the fluid and bleeding the system will do nothing to remedy the problem.
 

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1999 E55, 2001 E320, 1990 560 SEC, 2004 ML350, 2001 ML55, 1995 S500, 1998 SL500, 2010 E550 Sport zoo
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7,035 Posts
First things first.

Write down the VIN# of your ML and call the dealer to see if there are any outstanding recalls for power steering hoses on your car.

There is air that has gotten into your system, either from a leaking power steering reservoir seal, or as likely from a leaking power steering hose.

If no recalls, inspect the hoses where they run up into the cooler for any signs of leakage.


Also with a flashlight closely inspect the steering rack for any signs of leakage there as well, if air has been trapped down there it can really thrash a rack.

If no signs of leaks at the hoses (and/or they get replaced by the dealer under recall) and no signs of rack seepage, then:

If no leaks, yes, it would be best to replace the reservoir again (like $35) a couple of new bottles of MB fluid, and add 1/2 bottle of Lubrizol which is available from your dealer at/about $9 a bottle when you do the refill..

Then you must do the correct bleeding procedure from the start (without your car engine turned on, not even for a nano-second) and with the wheels in the air as high as is safe, pump that wheel back and forth until it gets progessively harder, to the pooint where you can hardly turn the wheel at all. This may mean more than 30 times, whatever it takes you need to get up to that almost impossible pointthat almost won't go any farther.

This procedure brings air up from deep down in the system, and with the Lubrisol which supposedly helps break up larger air pockets, and the fresh reservoir with screen - if there are not any leaks in the system you have missed, this should bring you to nirvana for a time.

Keep the beat !
 

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2001 ML320 & 2003 SL500
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Discussion Starter #4
Just bought my 2nd reservoir in a month. I am going to change & bleed this one myself instead of going back to my local shop.
Hope this will fix the noise...
 

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1999 E55, 2001 E320, 1990 560 SEC, 2004 ML350, 2001 ML55, 1995 S500, 1998 SL500, 2010 E550 Sport zoo
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Did you call your dealer to verify all hose updates have been done ? Have you checked for fluid leaks at the hoses and at the rack ?
 

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2000 ML 320 and 2015 GLK 250
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My Ml 320, year 2000 the power stering make noise, I keep top it up to stop the noise.
I found leak on my driveway, I need change the fuid container, and pump. Do you know any place who have a good machanic in Toronto, how much it will cost me.
 

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1999 E55, 2001 E320, 1990 560 SEC, 2004 ML350, 2001 ML55, 1995 S500, 1998 SL500, 2010 E550 Sport zoo
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Don't assume the pump is leaking - if there is a leak behind the reservoir, between the reservoir and the pump, then most likely that is a leaking reservoir o-ring/seal, and you replace the resertvoir at the same time.

Power steering pumps do go out, but it is much rarer than the seal/reservoir. A failing pump must be properly diagnosed 1st. There are aftermarket and/or rebuilt pumps that are somewhat affordable.

Please see the DIY at the top of this forum that will show you about this job. The parts and the MB power steering oil add up to under USD$100, however there is a bleeding procedure that must be correctly followed.

Good luck !
 

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2001 ML320 & 2003 SL500
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Discussion Starter #9
I changed the reservoir myself this time and still got noise from the power steering pump. The one thing I did notice is the when the truck is cold and I turn the wheel back and fourth all is good; no groaning noise. After the truck warms up for 5 mins - the graoning noise is there when you turn the wheel. Don't know what else to do besides change the pump again. I have check all the hoses and no leaks.
What else can it be?????????????????????????????
 

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1999 E55, 2001 E320, 1990 560 SEC, 2004 ML350, 2001 ML55, 1995 S500, 1998 SL500, 2010 E550 Sport zoo
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How did you bleed the system after you replaced the reservoir ?
 

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1999 w163 ML430 Australian Spec
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12 Posts
Technical Reasons for the Noise

The most common reason is air in the system, which causes cavitation of the pump.....and noise.

A worn/damaged pump. (cavitation will eventually damage a pump and nothing will stop the noise)

A worn/damaged steering rack. However, usually a different noise, when the rack is working hard at low speed and low engine revs.

The common annoying groaning noise is from the pump.........
Assuming the pump is ok (new or serviceable), then one must look for air in the system.
My personal preference is a new pump. "Rebuilt" pumps are just that, and they may have a previously damaged impeller from cavitation.

The air gets in during work on the system, or it can be introduced into the system while operating..... through leaks and/or aerated fluid.

All leaks, potential or suspect should be eliminated first. Check tighten everything in the system. If there is signs of leakage, investigate further.
If the reservoir or pump is disturbed/changed, replace the reservoir to pump O ring..........every time........and assemble the O ring lubricated with fluid.

The correct bleeding procedure MUST be followed WITHOUT the engine running, and keep the reservoir fluid level high at all times. (a low level can cause air to be sucked into the system).

After correct bleeding, check fluid level and start the engine.
Look at the fluid surface in the reservoir.
It should be calm.
If the surface is turbulent, the fine gauze membrane in the reservoir is damaged, and the pump will ingest air with the turbulent/aerated fluid.
Another reservoir is the only fix.

All air, and leaks must be eliminated before starting, or an air bubble can be expelled into the reservoir with enough force to destroy that new reservoir.

If the noise is fixed, but reappears after driving, air is being introduced.
Check again for leaks and fluid level. Be very suspicious of the reservoir to pump O ring seal.
Check for turbulence on the fluid surface. If the fluid is turbulent.......the reservoir gauze is damaged and it's time to start again.
 

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Discussion Starter #12
Believe I did the bleeding procedure right. I lifted the front wheels off the ground, put the key in pos one with out starting the truck. I turned the wheel all the way to the right and then to the left 50 times. The only other thing is that I bought a cheap rebuilt pump that I am going to have changed today with a new original pump. Let see what happens.
 

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2001 ML320 & 2003 SL500
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Discussion Starter #13
Well, All I have to say is I leaned my lesson with trying to get away cheap with a rebuilt power steering pump. I replaced the rebuilt pump I got from Auto parts warehouse online with a new pump from the Dealer and my power steering does not make a sound. That's one item off the list of repairs I have to do..
 

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1999 ML320
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126 Posts
RELATED THREADS

This thread is closely related to a couple of older threads. Anyone experiencing ps problems, or contemplating any ps system repairs should read all the information in these older threads. It will save you way more time, headaches, and cash than heading off in experimental directions! 43sqd has lots of good factory technical information. The pictures and pdf attachments in the other threads are worth thousands of words!

Here they are:

1. http://www.benzworld.org/forums/w163-m-class/1351110-help-replacing-power-steering-pump-11.html

2. http://www.benzworld.org/forums/w163-m-class/1552258-power-steering-pump-reservoir-2.html#post4747374

Good Luck!
 
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