Purchased this vehicle with 4500 miles January of this year. Even with low mileage, every service had been completed by an MB dealer based on time rather than mileage. Shortly after having it, I noticed that as the RPM's kick up there would be a matching intensity of a high pitched sound. The sound comes from the passenger side engine bay and my best description is that of an unbalanced fan blade cutting through the air. I replaced the serpentine belt with no luck. I took it to a local MB service shop who quickly ruled out an exhaust leak at the manifold and he thinks it may be the improper machining of the cams or the rockers which may be causing some chatter. I am hoping this is enough to prompt some possible suggestions before I turn this over for a FAT bill just to confirm his hunch. Any help would be much appreciated!

 

To be honest this sound most like the ball bearings in the alternator. can you hear the sound when the car is at idle?

 

I have never heard of improper machining of cams or rockers as an issue with these cars. That seems extremely unlikely. What about the belt idler pulley? Water pump? But a better description might help. Does it sound like it is from the front or the rear of the engine bay? Can you hear it with the hood open at idle, or are you basing the location from inside the car? Can you hear it all the way from idle to 5,000 rpms or only at certain engine speeds? Does the pitch change consistently with changing engine speed? Doe the volume change or just the pitch? How loud is it - very subtle or something anyone would notice instantly? If you can hear it while standing by the car with the hood open, does it sound like it's internal to the engine?


My car, while still under warranty, had a high pitched whine and vibration that felt like somebody was holding a dental drill against the car, but only as it passed by about 1,800 rpms. And only on warm days and with the air on. Turn off the air and it went away. After replacing a great deal of my AC system it was discovered to be a power steering hose. Now who would have ever been able to guess that?

 

Thanks for checking in Gents.

-The sound can be heard well with the hood open and closed easily.
-Comes from area around the cam cover and manifold.
-Generalized location is the same from inside the car or standing in front of it.
-Don't hear much of it at idle and becomes apparent at 2000+rpms
-Pitch and volume of sound increase with rpm.

Considering the low mileage I don't think water pump or alternator bearings could be the culprit but I'd rather be wrong as those seem like cheaper fixes. I thought it could possibly be related to the shaft balance issue but I hadn't noticed anyone complaining about a sound associated with it. Then again most didn't notice their issue until they had much higher millage.

 

First of all, this car has an M113 engine so there are no worries about balance shaft problems - that only affects the M272 and M273 engines.

Eliminate any of the accessory pulleys by removing the serpentine belt. It's OK to run the car for just a few minutes without the belt, just know that the alternator is not running so it's drawing on the battery for everything, and the water pump is also not operating, so it's best to do this with a cold engine. If the noise persists, then it's not a belt-driven pulley.

Your car has an early 722.9 transmission. These had a few faults, the most common were bad turbine speed sensors in the conductor plate. These will make a whine at idle (even in neutral) that tends to go away once in 3rd gear. You may also hear some "clicks" a second or two after shifting into D or R, or when coming to a stop or starting off from a stop. The solution is a $2K dealer visit to replace the conductor plate. Some of these can go years with no serious problems. Other will lock into "limp mode".

I do doubt there are any internal engine issues. Of course anything is possible, but those are very, very rare on these engines. I know it may be hard to do, but sometimes it's best to just "turn up the radio" to solve the weird problem noises.

 

Hey Rudeney,
First - Thanks for the steps to rule out accessory items! I swapped the serpentine belt myself so this will be easy to do.
Second - I provided my VIN to an MB service guy over the phone at a earlier today and asked him to confirm my Engine....he says its a "M272". Is there somewhere to check and confirm this with 100% certainty? perhaps on the car as well to compare with a registry?

 

I guess a follow up question is what warranty would you trust? Maybe time to invest considering the tranny issue you mention. : /

 

Please post your VIN so that we double check which engine it truly is.

 

WDBTK75G16T065905

 

Your car's engine info: 113968 30 725457

Your car's transmission info: 722901 00 465085

 

Thanks Xsever! I don't know why that MB Dealer service writer would tell me otherwise outside of setting me up for a bigger service. I hate thinking that way of people!

 

Yes, of course it's an M113 - all MY2006 CLK500s are! Service writers are commissioned sales staff. Just as the sales staff on the car lot side of a dealership are paid commission when they sell cars, the service writers are paid commission when they sell services. Honestly, I am surprised that your service writer even knew the term "M272 engine". Most are doing good to understand the difference between a V6 and a V8.

 

The verdict is in from one of the area private MB service shops.....The sound is believe to be caused by camber shaft chatter due to striations that apparently came machined this way. Apparently this is nothing to be concerned with mechanically. I guess I'll have to get used to having a minor "turbo spool" sound as I rev up. We'll see how this goes but certainly chime in if you have other thoughts on the matter.