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Our first 10,000 miles on our Metris as a great experience. As the vehicle was 1 year old we had Service A completed. Because my wife didn't know what the service included, she approved 'Service A+' or something that sounds similar. Apparently that involved "oil treatment before drain and in new oil and fuel treatment. Besides the fact that is all unecessary, I think it may have done damage. The dealer reimbursed us for the unwanted "treatments". Why would a fully synthetic oil and premium fuel vehicle need this at 10,000 miles?....Ripoff!

The problem is that we hear a very loud intermittent tapping under the hood. After several return trips to dealer and oil filter change at their expense, no change. Dealer service explains that the fuel injection is the sound which is normal for the Metris.

Our Metris was fine before the service, totally quiet and enjoyable to drive. The Metris is my wifes everyday driver. She loved it, now she says she's embarrassed to drive it because of the noise.
 

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1) God. For years I have been espousing the honesty and integrity of Mercedes dealers. I now wish to exhault the honesty and integrity of Contemporary Motor Cars of Little Silver, NJ, and renounce my statements regarding the dealer body as a whole.

2) The cleaning BS is an old service ploy, invented and pattented by Ye Olde Jiffy Lube in 3200 BC. It involves pouring in some detergent and running the engine briefly for a few moments- it does have some benefits if you are using non-detergent oil, but all modern oil is detergent (by modern, I mean after the start of the Truman administration). It has no inherent disadvantage unless you pour it in and don't change the oil and we're previously using non detergent oil- in which case it will cleanse your engine's accumulated gunk right into the oil filter and jam it. (Detergent oil does the same thing, except slowly over time, and is why you need to change the filter- prior to detergent oil, many cars didn't have filters!) It also has no benefit what so ever, so it is a waste of money.

3) Common-rail Direct Injection gas engines have an ignition cycle not that dissimilar to a direct-injection Diesel engine, except the final ignition is done using a multi-fire spark plug rather than pure compression. As a result such engines are fairly loud, suffer from the same "rail chatter" as a diesel does, and make similar (though ever so slightly quieter) sounds.

The solution to this noise level is better encapsulation of the engines combustion noise, especially to the cabin. There are two possible causes to the problem- one, you had the noise all along and just now have noticed it, or two somebody botched the reinstall Of one of the noise blockers.

Unless this noise is insanely loud, the M274 engine (and all other small displacement Direct Injection Turbos like it) is just a noisy engine.
 

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Discussion Starter #3
I'm betting you hit it. We purchased our Metris in April 2016. Here in North Florida is around 80°+ during the day. I supposed that the AC covered the noise, which you are confirming my suspicion. It was around September/October when the service was done and we ran the van without AC for the first times.
Thanks for the input.
 
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