Mercedes-Benz Forum banner

1 - 14 of 14 Posts

·
Registered
Joined
·
162 Posts
Discussion Starter #1 (Edited)
M112 High RPM Wobble/Coarse Noise

Greetings everyone,

About 6 months ago, my car developed a "wobble" noise when in 3rd and 4th gear and with the RPM above 3-4,000 especially when driving uphill. It's definitely an engine noise.

Car has 170,000 (106,000 miles) km on it and I change the oil every 6,000 km (3,700 miles) with 229.5 oil and fleece filter. The power and fuel consumption are very normal and there are no errors when scanning with STAR.

In another thread, I detailed a "lifter tick" noise that I've been getting when the car is warm and in D or R with the brakes applied. If relevant, the thread is here: http://mbworld.org/forums/clk-class-w209/634231-m112-engine-knocking-sound.html

I am attaching an audio clip I recorded with my phone last night with the car in 3rd and 4th gear and with the "wobble noise" very clear.

I did some research online and is this the harmonic balancer going out? I doubt it since the car is a 2005 and by then the issue was fixed on the M112/3 engines.

Looking forward to your opinions on this.

Thank you in advance.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #2 (Edited)
Just read this on another thread:

I should mention that the engine was making a slight knocking sound that would come and go, I suspected the lifters at first but the knock was coming from the lower front part of the engine, thats when I saw the Harmonic Balancer pulley sliding back off the rubber.
Seems the lifter noise I have is also related to the harmonic balancer! The person changed it and things worked out for him after that.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #3
Here is what the harmonic balancer on my car looks like in idle:

 

·
Coupe/Convertible Forums Moderator
Joined
·
18,833 Posts
That looks normal to me. A minuscule up/down movement is just the effect of the rubber isolator doing its job. What you don't want to see is a front-to-back movement of the ribs on the pulley.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #5
That looks normal to me. A minuscule up/down movement is just the effect of the rubber isolator doing its job. What you don't want to see is a front-to-back movement of the ribs on the pulley.
Thanks a lot for the input. Any opinion about my initial post and the sound clip I linked?
 

·
Coupe/Convertible Forums Moderator
Joined
·
18,833 Posts
It's hard to tell. It sounds more like a rattle to me. It could be any number of things. I;d get a mechanic's stethoscope and (carefully!) start listening.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #7
It's hard to tell. It sounds more like a rattle to me. It could be any number of things. I;d get a mechanic's stethoscope and (carefully!) start listening.
So after using a mechanic's stethoscope, the lifter/tock tock sound is coming from here:




Any suggestions as what to do next? Just remove the valve covers and start changing parts?
 

·
Registered
Joined
·
162 Posts
Discussion Starter #8
The problem with the high RPM wobble was a worn transmission mount. Replaced it and all is back now to buttery smooth.
 

·
Coupe/Convertible Forums Moderator
Joined
·
18,833 Posts
Good deal! While you were in there, did you check the flex discs on the drive shaft?
 

·
Registered
Joined
·
162 Posts
Discussion Starter #10
Good deal! While you were in there, did you check the flex discs on the drive shaft?
Unfortunately, no as I forgot to ask the mechanic to check them while he was changing the mount. What are the symptoms for when the flex discs start going bad? Vibrations right?
 

·
Coupe/Convertible Forums Moderator
Joined
·
18,833 Posts
Visual inspection is best. Just look for dry rubber and cracks. Unfortunately, when they start making noise or vibration, it's probably too late.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #12
Visual inspection is best. Just look for dry rubber and cracks. Unfortunately, when they start making noise or vibration, it's probably too late.
Too late to replace them or too late as in they'll cause destructive damage?
 

·
Coupe/Convertible Forums Moderator
Joined
·
18,833 Posts
Too late as in by the time they make noise, they will likely disintegrate very quickly. This is why flex disc inspection is part of the B service.
 

·
Registered
Joined
·
162 Posts
Discussion Starter #14
Too late as in by the time they make noise, they will likely disintegrate very quickly. This is why flex disc inspection is part of the B service.
I'll have him inspect it soon then. Thanks for the reminder!
 
1 - 14 of 14 Posts
Top