vmaddon

My CLK55 just turned 40k. On cold start, there is a noticeable groaning noise coming from the engine / transmission area. As the car runs for a few minutes, the noise gets less noticeable, but never leaves. I can best describe the noise as that from a weak comporessor or PS pump.

OK, must be a tensioner, pulley, or belt drive device.
To troubleshoot the source, I pulled the serp belt. How fun is that
Anyway, to my disappointment, the noise remained the same.

The only other source I can think of is the trans.

Now, I would suspect that a proper trans fluid / filter change would be the best place to start, especially since I expect that it is original.
But looking beyond that...

I have 2 questions.

1. Has anyone had a similar experience they wish to share??

2. How different ( expensive ) is the AMG CLK55 trans from the 430???

Any other suggestions appreciated as always.

Thank you

Vince

TMAllison

Put a big rubber bushing or something soft on top of your floor jack, stick it under the oil pan, fire it up and then carefully pick up some weight with the jack and see if the groaning dissappears. If it does its probably a motor mount.

Dont lift more than 1/4" or you might damage the fan blades, intake and/or exhaust connections.

Mbtech22117

oil pump?

Brabus C55

if it sounds like a PS pump, why isn't that (mine's loud at times). it can be tough to describe sounds ... been there done that w/ my friends & my wife..."it sounds like what???"

is your sound "engine speed dependant" or "road speed dependant" (does the sound change w/ every gear shift or does it change as you go faster regardless of what gear your in)?

vmaddon

I was hoping that was it, and that is why I removed the accessory drive belt first. With the belt removed, the noise remained the same.

The noise follows RPM, in neutral, drive, reverse, and while driving.
Honestly, it does not change significantly in drive vs neutral, nor with engine load.

The noise will get a little louder as the RPM approaches 2k, but levels off from there.

Any help is appreciated and thanks.

Vince

Gullwing

When the transmission pump goes it is a high pitch noise that changes with rpm, and is present in P R N and D.

Brabus C55

when you say say the noise follows the rpm ... does this mean every time you shift the noise resets and starts again?

have you verified fluid levels are correct?

vmaddon

I sincerely appreciate the interest and help that all of you are providing.

Yes, the noise does rise and fall with the rpm, so it will drop in frequency upon a shift. It will then climb until the next shift, and so on.
Once road speed picks up to over 25-30 mph, the sound pretty well is drowned out.

It would appear to be a classic belt driven device noise, if only it would have stopped with the belt removed.

As far as the pitch, I would not consider it to be a high pitch.
From a frequency standpoint, I would estimate about 150 Hz at idle.
I base this on its relative pitch to a 100 and 200 Hz test tones.

As far as fluid quality and level, the car is new to me and the "sealed" trans is a problem. I have not gotten around to purchasing a dip-stick tool to check the level. I assume that the on-board diagnostics cannot detect trans fluid level.

Are there any tricks for a coarse reading as a sanity check??

Thanks again

Vince

vmaddon

Thanks again to all.

I tried to lift the motor, as per TM's suggestion.
There was no difference in the noise, so I continued to look on.

I then broke the sacred seal and checked trans fluid with a cable.
I have about 2 3/4" of absolutely perfect looking, and tasting, fluid.
The more I listen for the noise, the more it appears to be coming from the front of the engine.

Since I had the belly-pan off, I crawled under with the motor running.
Again my ears lead me to the front of the motor.

But, the noise continues with the belt off.

Only 2 things I can think of is timing chain or the oil pump as per MBTech's suggestion.

Any suggestions as to attempting to diagnose further???

Also, if its either, is this likely a sign of impending failure or just the car's unique persona??

Again, thanks to all for your help.

Vince