Should my engine sound like that? - Mercedes-Benz Forum
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#1 (permalink) Old 05-25-2010, 08:45 AM
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Should my engine sound like that?

I am new to MB as of December so it's just a sound I'm not familiar with.

As I work my way through some issues with my recently purchased CLK55 I am curious about the sound of the engine. When I start it cold I can hear a "whine" that will reduce significantly in a few seconds but than stays constant. It's hard to describe but it's not a squeeling belt, bearing knock, grinding or fuel injector click. It rises and falls with engine speed. Somewhat mechanical like a gear.

I am reasonably sure this is not coming from any of the pulleys as I have used a stethoscope on each. The sound cannot be pin pointed to a specific side of the engine but from underneath it is most clearly heard from the front of the oil pan so I'm thinking either oil pump or timing chain. (the fact that it goes away after a few seconds leads me to believe it may be related to anything that needs to be lubircated or build up pressure.)

The car runs great and this may not be an issue at all but I'm mostly curious if there are any known issues like a timing chain, tensioner or noisy oil pump as I imagine any of those would be costly if a complete failure occured.

Any thoughts on the matter are appreciated.
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#2 (permalink) Old 05-25-2010, 05:13 PM
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It's a bit presumptious of me to reply as I do not own a CLK55, but I think that the sound is most likely to be the timing chain - when cold. I seem to remember that my M112 engine initially whines, but it soon quietens down as it warms up.

I'm sure that it is nothing to worry about, but I also would be interested to hear the views of another CLK owner. Even better, an MB tech who knows the car backwards....
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#3 (permalink) Old 05-26-2010, 12:49 PM
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I am curious to hear what others have to say as well. I recently got a CLK 320 and I experience a similar noise. Mine sounds like a power sterring typoe of whine, but the fluid is full. Any help will be greatly appreciated.
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#4 (permalink) Old 05-26-2010, 01:30 PM
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I had the same problem for the last year on my 06 CLK 500. It was a whining sound that went with the RPM. Two local dealers had it for over two months looking into it. One had it for 6 weeks and replaced the oil pump twice (sound was supposedly coming from the oil pan, the power steering pump and rebuilt the bottom of the engine. It didn't fix the problem. Took it to an independant guy, and he found a Service Bulletion out on these cars that indicated the AC Compressor Pulley was known to have problems. There is an easy way to test this... they have a test belt that removes the AC compressor from the system and if the sound is gone, that is your problem.

Now my car sounds normal again.. these engines are quiet.. the only sound I hear is the sound of the exhaust.

I can give you the bulletin number.. and also scan it for you. It gives you testing procedures and replacement part numbers.

Just let me know.
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#5 (permalink) Old 05-27-2010, 04:47 AM
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Thanks for the info. I'll think I'll pull the belt tonight and start it to see if the noise goes away. That would a least tell me if the sound is internal or external to the motor. It shouldn't need to run for more than 30 seconds to know. I'll take that bulletin if you have it.

Did the sound change when the A/C was on? I don't notice any difference.
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#6 (permalink) Old 05-27-2010, 06:42 AM
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WATERLOVER, Please put a link on this site so I go to the info you have on the A/C belt. My wife's CLK320(2005) sounds like a jet plane outside the car when the A/C is on. Normal sounding engine with no A/C running. Thanks,
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#7 (permalink) Old 05-27-2010, 07:56 AM
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Quote:
Originally Posted by geezergolf View Post
WATERLOVER, Please put a link on this site so I go to the info you have on the A/C belt. My wife's CLK320(2005) sounds like a jet plane outside the car when the A/C is on. Normal sounding engine with no A/C running. Thanks,
hey geezer...I believe that the sounds coming from the car sounding like a "jet plane"...are normal...my 05 c230 made the same sound...and my 04 clk55 sounds no different. hopefully, keyhole will correct me if i am wrong...but that "jet plane" sound should only be on when your a/c is on. and i'm pretty sure that's the way it's suppose to be.
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#8 (permalink) Old 05-27-2010, 09:14 AM
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geezer... actually the jet plane sound is normal believe it or not. Mine does it when the AC says max ac (can't remember the exact wording). The sound goes away once the interior temp is cold enough. When I first heard it, I thought it was a tornado siren going off. It was actually a funny moment. When I talked to the dealer and a couple independant shops about it, they all confirmed that it is normal. Benz did it so that the interior will get colder faster. I had my temp set at 72 and on hot days when I turned on the AC it did it every time. I played with it a little and changed it to 74 and it doesn't do it as often now.

rnettleship ... I don't think you are able to take off the belt and test unless you have the test belt. You need to have a belt on the car in order for it to start... but maybe I am wrong. I will post the TSB tonight for you. Also it didn't matter if the AC was on or off. It was constant and just went with the RPM
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#9 (permalink) Old 05-27-2010, 09:51 AM
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I would be surprised if the car wouldn't crank and start without the belt. Of course it would not charge the battery or pump the coolant but I would only let it run for about 15 seconds. I bet the dash will light up with lots of warnings as well. I'll let you know how it goes.
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#10 (permalink) Old 05-27-2010, 11:06 AM
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Originally Posted by waterlover112 View Post
There is an easy way to test this... they have a test belt that removes the AC compressor from the system and if the sound is gone, that is your problem.
Interesting... but it is hard to figure out how this 'test belt' is supposed to work, if you study the Poly-V belt running diagram below. With the a/c compressor pulley left in place - how can the test belt avoid it....

Unless the test belt only encloses only items 1 (crankshaft), 4 (guide), 5 (generator), and 6 (coolant pump/fan). If it could be tensioned, that could work.
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File Type: pdf W209 poly V belt.pdf (155.7 KB, 157 views)
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