Knocking/clacking noise on 12 ML 350 during cold start
 

I just purchased a new 12 ML 350 and just has 700 miles and I just noticed an annoying knocking/clacking noise during cold starting inthe mornings. It is louder in the garage probably due to the noise bouncing off the walls but can still hear it when it is parked outside. The noise seems to go away when the car warms up. This car costs over $50k and it makes knocking noises??? Does anyone know if this is normal? I tried to go test drive another new ML but all the dealerships in houston are sold out..would appreciate any input.

Is it a Bluetec?

3.5 V6
 

No, its the 3.5 V6 gas. Have only fueled it up once with 93 octane at Shell.

kind of like a very quick but punctual ticking noise?

if so, that the new direct injection...get more power and more efficiency, but it runs under super high pressure (similar to a diesel), so when the engine is cold, the noise is more pronounced. nothing to worry about.

That's exactly what it sounds like. Do you know if all the new 350s with v6 engines make the noise or is it random? i want to go test drive another one or a 2013 and see if they make the same ticking noise. Want to know before I go and hunt one down..thnks

yes they all do...as I said, it's a function of direct injection...running as much fuel pressure as a diesel pretty much. to be honest I like the noise - sounds awesome...feels like theres actually something under the hood. before, you wondered if there was a hamster peddling under the car to move you forward....

this high pressurization is what allows the engine to be so fuel efficient, while at the same time be more powerful than the outgoing engine (piezo fuel injectors).

two things are to blame here: 1) government regulation for fuel efficiency and 2) consumer demand for more efficient and more powerful engines.

this is not manufacturer specific....all di engines will have a similar if not identical problem at startup.

hopefully you will rest easy now! :y

It turned out that the clacking noise is not normal. My ml350 has been in the mb shop for a week and cant find the problem. The technician said they may need to replace a piston or even the entire engine. I told them that if they do that that I deserve to get a new replacement ML350. The dealership is waiting on mercedes benz response on whether to fix....fix what??they dont even know where the noise is coming from....has anyone ever gone through a situation like this?

I would much prefer a new engine put in by the dealership than to have a dealer's tech tear an engine down and replace a piston. MB typically has great customer service, so push for that service. Have you seen the Chevy program where you can return the vehicle if you're not satisfied? Tell them you want to pretend its a Chevy and return it for another that works :-)

In the grand scheme, this sort of problem is pretty rare, so they should be happy to go way out of their way to satisfy the customer.

My brand new C63 did the same thing when I got it. It was actually due to the oil level being low...right from the dealership. Imagine that, I picked up my new car and there wasn't enough oil in the engine. Never trust anyone, check everything when you get your new car home.

If they are talking about replacing a piston, your engine could be the victim of the dreaded "piston slap," which occurs when a piston bangs sideways into its cylinder wall because the piston is undersized compared to the cylinder bore. As the engine warms up, the piston expands and the noise disappears.

GM engines are notorious for this, but of course, GM says it is "normal." But over time, piston slap can scuff the cylinder wall and lead to increased wear.

A new Mercedes should never leave the assembly line, drive to storage, get put on a train and shipped to a dealer, where it is prepped by technicians for delivery and NOBODY catch such a major flaw....
Just saying.

Well MB is going to call me today to discuss my complaint on not to replace the engine and that we should get a replacement vehicle. I have a list of why it isnt fair to us to have engine replaced. Does anyone have more input that i should bring up to MB?? Hope no one has to go throught this stress.

If engine is replaced:
1. Vehicle will depreciate.
2. Engine id number wont match with vin.
3. Have to disclose if i decide to sell vehicle later on.
4. MB hasnt located problem so it maybe sometging else.
5. How many times have you had to replace engine on new vehicle with only 800 miles.
6. This vehicle is a lemon!

Appreciate any input..

Number Match? UR kidding right? Depreciate with "new" engine can't be worth less then it is now.
They won't give u a new ML be glad they want to replace the engine.

Mine does the same. It's the high pressure of the direct injection, unless you have some wierd anomaly. This is an aea of industry research, as you can see from this: http://delphi.com/pdf/techpapers/2011-01-1216.pdf

Keep reading Greg, dino engine is toast

Engine replacement in new ML
 

Yes, number matching is a non-issue. This is not a vintage collectible. Not sure if your really need to disclose. Anyone interested in buying would have access to service records, I assume. My '06 had the engine pulled for the balnce shaft sproket replacement at about 60k miles - ran great until I sold it a couple years later. My '02 M3 also had the main bearing replaced fairly early, and had no other issues. I can uncerstand your feeling, but unless you can lemon it, I would accept the offer and get on with enjoying driving.