My ML320 has suddenly developed what sounds like the old valve tap you used to hear on old american cars - is this unusual? With foot on the gas and accelerating the noise is clear, foot off the gas or lightly on to hold speed you don't hear it.

I looked the vehicle over last night and found nothing loose or vibrating; thought it might be a belt slapping or loose mudflap, but that's not the case.

Thoughts please, thanks.

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Francis E. Abate
Automotive Restoration & Preservation
Sheet metal, trim and upholstery

I had a simular problem last year at start up. It would go away after warm-up. At the time I was using Amsoil 0W-40. Once I went back to Mobil1 0W-40 the noise went away. My 2 cents.

Check your harmonic balancer, it might be coming apart.

I still use Mobil1 0W-40 though its time for a oil change.

Harmonic balancer - the pulley for the crankshaft? Could you expleian a little more what might be happening, thanks guys.

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Francis E. Abate
Automotive Restoration & Preservation
Sheet metal, trim and upholstery

Some information here on the HB M112/M113 Harmonic Balancer Recall If you do a search on Harmonic Balancer you'll find tons of information. It can be a real big problem if it fails while your on the road. My 2 cents.

I checked under the hood with the engine running and the sound is clearly coming from the passenger side valve cover or cylinder head - have not put a screwdriver / stethoscope on it to pinpoint exactly.

This would not be an indication of the harmonic balancer falling apart right?

Any other giudance appreciated!

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Francis E. Abate
Automotive Restoration & Preservation
Sheet metal, trim and upholstery

Don't think so, if it was the HB the sound would be up front. I would do an oil change and see if that helps. My 2 cents.

Get your oil changed and the "tapping" noise will soon disappear. I had the same problem the oil was at the end of it's life cycle.

-Kevin

Kevin - I'll be changing th oil this week. I did run it by my local mechanic and right away he believes its an exhaust leak near the manifold which both my son & I concluded as well earlier the week. As I think about it's probabaly more of a air type fluttering sound than a tap so we'll see.

I'll let you know which of these it turns out to be.

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Francis E. Abate
Automotive Restoration & Preservation
Sheet metal, trim and upholstery

What year is your ML?
Is it a 320 or a 430?

We had problems with the rockers making a racking noise and replaced tons of them under warranty?

I am familiar with the engine tick noise going away after warm up or a fresh oil change, but if a fresh Mobil-1 oil change does not do it, you may want to look into getting the rockers replaced.

It is a very simple job that requires removal of the valve cover and removal of the rocker shafts and placing the rockers on a special jig that holds them in place while you take a steel rod and push the old rockers off the rocker shaft and put the new ones on one at a time.
Then you put the shafts back on, torque the bolts, put a new v/c gasket on and you're D.U.N - done!

It's actually a fun job to do if you got all the special tools of course.

Usually the noise would come from the drivers side only, in most cases and we replaced quite a few sets of them at the dealer.

I notice it on all my mercedes. If I have not drive it for a month or so. There is tapping at startup. What I try to do when starting my car when it has not been running in a while is to "jog" the engin. Jog meaning turn the key let the engin crank and then turn of the engine with the key, wait ten sec then repeat for 3 times. This reduce or eliminate the tapping sound.

But if I drive it regularly like everyday taping does not happen.

My conclusion is that my taping shound is comming form the oil not getting the lifter in time. So changing oil may help.

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Silver Honda Accord, 2006
Silver G500, 2003
Silver SLK-320, 2002
Black ML-320, 2000
Bule Porsche 993 Targa , 1997
Silver Merkur XR4Ti, 1987

I don't know if this is your issue, but I noticed a tapping sound as well that went away after a few minutes. Is your tapping sound always happening or just when cold.

My sound happened first thing in the morning when I started it. The MB mechanic said it was an air compressor that pumps air (for it's oxygen content) into the exhaust for the benefit of a cold catalytic converter (helps converter burn more efficiently when it's cold). Once the exhaust heats up the compressor goes off. The location of the noise was roughly where you hear it.