I have 70,000 miles on my GL 320 CDI. About 6 months ago I noticed there was more than usual vibration at idle (600-700 rpm). Lately it has gotten worse, and also seems to be increasing (and moaning) around 2000 rpm. You can lay your hand on the engine, or grab hold of the chrome tip exhaust, and the vibration is strong enough if feels like your hand is asleep. Not a technical diagnosis I know, but it is excessive. My first trip into the Benz dealership, they claimed an idler pulley was bad...but it made no difference at all. I then went to an independent Mercedes shop, and they replaced the engine and transmission mounts. Still no difference. Back to Mercedes, and they disassembled the exhaust system (per corporate recommendation) and re-assembled, and still no difference. So, we drove it to Winter Park, CO, over Thanksgiving, and the water pump froze up. A 100 mile tow to the Denver dealership, where they replaced the water pump, and also said the idler pulley the local Benz dealership had just put on..was bad. Got it back, and still no difference. I am at my wits end. After much internet research, I'm inclined to think that the crank pulley with harmonic dampener is bad (or the dampener has slipped)...or possibly the torque converter is bad. I have never had a water pump go out on any vehicle with less than 150,000 miles. I am concerned that the vibration has caused, or will cause, many additional problems, including a cracked crank, or leaky main seals. I've had 3 Lexus sedans, and should have stayed with them, as they NEVER caused me any problems. I'd like to find an old experienced diesel mechanic (as opposed to another young service tech). And by the way, I compared the vibration to an ML 320, and there was no comparison. Any suggestion please. Thanks. Jim

I am starting to notice this idle vibration as well on my ML. 138000 miles. It feels like a heavy harshness at idle, and usually happens about when the engine has just warmed up. Cold it sometimes feels fine, where you can't feel the engine running, but shortly after warm up, at idle, the harshness returns.
Also it will only do it every so often.
If you hold the brake pedal and apply enough throttle to raise the RPM's about 100-200RPM's it goes away.
My first instinct was a bad tranny mount, but as I said above, it only does this harshness intermittently.

Plutoe, will try the conditions you mentioned and see if it makes a difference. The answer to your first question is no.

How is letting the OP know that they are not the only one, and that an ML320 owner has a similar issue, a hijack?

Does any one check the fuel system - those piezo injectors can be checked (adaptation values) using Xentry w/o taking them off in opposite of the old type, also leak test? From all it sounds like internal engine problem - did V6 engine have balance shaft?

Are we at school again ? Yes or No .Christ......no wonder JIM has not replied!!

I guess he is trying to replace 240D........

No laser temp pencil.


My cousin in head mechanic for a large trucking operation here in IN. He said he's positive it's an injector.


SORRY ALL FOR NOT RESPONDING. WE MOVED...AND EVERYTHING ELSE WAS PUT ON HOLD. Would really appreciate follow-ups.

With the factory software (DAS) there is automated test for the injectors which will tell you if any particular cylinder is working more or less than the others, like a cylinder balance test. This test is a good way to work out if and injector is out of balance from the rest and causing the rough running.

watch the crankshaft pulley, is it smooth spinning or does it wobble at idle? Does your serpentine belt run smooth or shake at idle? I have seen both problems, one the crank damper and the serpentine tensioner fail.
Have a dealer run the cylinder balance test/adaptation, several have had it done in the past and reported much less engine noise/smoother afterwards.

I've had everything checked per the above, but nothing has lessened the vibration. I just had it checked by a Denver Mercedes dealer, and they said the vibration is within operational tolerance, although it was more than normal. I am quite convinced if anyone on this forum were to lay hold of the exhaust it would be apparent the vibration is not normal, and is capable of compromising longevity in many ways. In fact, at 79,000 miles, I am having to replace the steering hub for 2nd time (first time was at 32,000 miles), and oil cooler..total bill $4500. Luckily, I have a service contract and my copay will be $200. I love driving this vehicle, and the fuel economy is unreal for a full-size SUV (27-31 mpg hwy). But there is a problem, and I will sell it before the warranty contract expires if I can't find the solution..as I am forced to choose that this is a trend. My wife wants me to keep it, and says the bugs are getting ironed out. She's a gifted nuclear test engineer..and I'm surprised how often she can choose mechanical options correctly. But I think the evidence may lead to a litany of problems. Would appreciate any help. Thanks. Should have bought a Lexus 470.