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  #1  
Old 03-15-2015, 06:18 PM
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Join Date: Oct 2010
Location: Bradenton, FL
Posts: 10
'06 S500 making power steering like noise

Hi all,
My S500 is making a noise which is quite loud. A few facts:
I was the first vehicle at a light in the middle lane and realized that I needed to take an onramp which was about 80 yards ahead on the right. When the light turned green I stomped on it to get safely ahead of the vehicles to my right so I could move over for the ramp. After switching lanes I came off the gas and hit the brakes for a quick bleed of some speed and the engine shut off. All of the warning lights were on and I couldn't restart the engine for I have Keyless Go and when I put it in neutral and tried hitting the button while stepping on the brake pedal nothing happened. The key was in my pocket. I pulled off to the side of the ramp, came to a full stop, inserted the key and she started right up. I proceeded back on the road and continued down the highway for about 15 miles, took the exit and came to a stop at a set of lights. It was at that moment that there was a very loud noise which sounded just like a bad power steering pump. So loud that the driver next to me rolled down his window and pointed at my car.
I took the car home and began looking under the hood. First to the power steering pump which looked ok and had fluid. I took a large screwdriver and began listening to various units to see if one was noisier than the others. All seemed ok. I removed the serpentine belt and started the car to confirm any of the units making noise and the noise was still present.
I removed the engine cover and the noise seems to be louder from the center and toward the back of the motor. Almost as though it is emanating from around the firewall area and underneath.
Any thoughts on what it may be? All systems seem to work and there are no warning lights on.
Frank

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  #2  
Old 03-15-2015, 11:11 PM
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Join Date: Jan 2012
Posts: 7,534
You have quite a mix of things going on.

Hard accel should not have stalled the engine unless the fuel filter is very clogged or fuel pump getting weak and you never drive at high load / speed. ( RE you have always been driving at low fuel consumption so you never noticed at issue. )

The noise could be transmission pump buzz ( just like a PS low on fluid ) This could be caused by low fluid level or a filter that is clogging.

The stall can't restart is an object lesson on why I don't like push button start. Keys are tactile and their operation unambiguous removing the need built in safety controls.
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  #3  
Old 03-16-2015, 05:18 PM
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Join Date: Oct 2010
Location: Bradenton, FL
Posts: 10
Quote:
Originally Posted by 97 SL320 View Post
You have quite a mix of things going on.

Hard accel should not have stalled the engine unless the fuel filter is very clogged or fuel pump getting weak and you never drive at high load / speed. ( RE you have always been driving at low fuel consumption so you never noticed at issue. )

The noise could be transmission pump buzz ( just like a PS low on fluid ) This could be caused by low fluid level or a filter that is clogging.

The stall can't restart is an object lesson on why I don't like push button start. Keys are tactile and their operation unambiguous removing the need built in safety controls.
Sounds as though if it is the transmission pump it is nothing I can replace because from what I've read the 722.901 transmission is not serviceable unless done at a MB shop because the fluid needs to be pumped into the unit because there is no fluid tube. Correct??
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Old 03-16-2015, 05:21 PM
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Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 13,648
Quote:
transmission is not serviceable unless done at a MB shop
That is an incorrect statement. Find a good independent that knows how to service one of these transmissions and you will be fine.
__________________
Jim
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  #5  
Old 03-16-2015, 07:06 PM
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Whatever happens, please post the solution to help others.

Low fluid makes pumps buzz due to cavitation ( air bubbles / pockets of vacuum that open then collapse. ) In the near term the pump won't be damaged and won't need to be changed.

Checking the fluid is more involved, if you don't have a way to lift the car level it will have to go to a shop. I " think" this trans was also used in Chrysler products so a good domestic shop should be able to help.

Doing some searching, this trans has a standpipe in the pan and what looks like a drain plug but really isn't. The trans is run to a specific temperature ,plug removed. If a slight bit of fluid dribbles out, the level is good. To add fluid it must be pumped through the standpipe plug. Get creative here, turkey baster, tip from a gear lube bottle screwed on the trans fluid bottle. ( Might not work with MB factory fluid / some large cap USA bottles )

There is apparently an uprated pan ( +3 mm deeper sump , taller stand pipe for more fluid )

Regardless the pan should come off the trans at some point for a look and fluid change

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