Hey everyone- lurker here that needs some help!

Long story short- we purchased our first GLK350 (a 2012 with 24,000 miles) about two months ago. After having it for two weeks my wife was on her commute down a highway to work, a tacoma spins out going too fast on ice the other way, spins into her lane and hits her head on. She was very lucky, and the GLK kept her injuries minimal considering the impact and that the other driver had to be extracted with the Jaws of life and life flighted. My wife has suffered a shattered heel and ankle but that's it. She credited her well-being to the GLK and naturally wanted another...SO


We found a new replacement- a 2013 GLK350 4matic with 30,000 miles. I flew to Denver, picked it up, and drove it back same day. Well Monday morning when dropping our little one off at daycare I got out of the car while idling (first time I had heard it run warmed up at idle), and there was a very loud and obvious tick / knock emanating from the bottom of the car (sounded like a bad exhaust link or jacked throw out bearing on a manual car). Well I get home, pop the hood with the car idling, and WOW it's a loud knock. I swear I thought I bought a diesel for a second. I get out my stethoscope and isolate the sound the rear passenger side of the manifold.

Of course the dealership is claiming they heard nothing, and said to contact Mercedes of America- They say don't drive it, and send a tow truck to pick up the car (at 10:30 at night). The nearest dealership to us is Albuqurque, NM so the car gets taken there (4 hrs away). WELL... service manager calls today and says "sounds like normal injection sounds to us -we hear nothing abnormal." How did I know they were going to say that?? Luckily I grabbed a few videos of the knock before sending off the car- here is one of them. Does this sound like normal injection sounds to you? I know our last GLK didn't sound like this at idle.

Thanks for any help or insight you can offer. At this point we are so frustrated.

http://vid38.photobucket.com/albums/...psoocr19kc.mp4


Sounds more like a dying lifter to me. The fact that it gets louder as the car reaches operating temp seems to support this theory- but hey what do I know?

 

Yep, sounds normal to me. It would be more quiet if you closed the hood.

Your 2012 was the M272 engine - old port injection (and quiet). The 2013 has the new M276 engine with Direct Injection. I've never encountered a DI car that didn't like that, even BMW or VW/Audi.

 

I've got a 2014 350 GLK and the sound at idle certainly is not very refined. Sounds like a "lame" diesel. Don't mean that as any put-down of Diesels. I prefer the idle sound of the Diesel GLK, actually. The sound of the later 350 GLK engine gives the impression it can't decide if it's a gasoline engine or an oil burner.

I've heard the earlier 350 engines at idle, like you had, and they sound more Mercedes-like.

My understanding, also, is that it's down to very high pressure of the D.I. system. Might make troubleshooting engine noises harder later on in the life of the vehicle with all that standard noise going on...

Having said that, I think it's really hard to locate the source of or legitimacy of noises when they're recorded and then played back via the Internet etc. Peculiarities of microphones, recording locations, recording levels, having the hood open like spyked mentioned, speakers used for playback, playback levels etc. In-person listening can definitely be another matter.

 

Unfortunately, you did not rev the engine during the video. If the sound smooths out at higher rev's, it is the normal direct injection system sound. You did not say it threw a code and having only 30,000 miles, it is still under original warranty. Was it bought from a MB dealer with extra warranty? Do you have a history report? Why was the car traded?
If this is a case of Lower end problems, it won't last to the end of the original warranty so that should cover you. If it is a valve train problem, you would have poor performance. It does not sound like a vacuum leak or an exhaust problem. However, since the insulation keeps you from hearing it while inside the vehicle, and you have not complained about performance I would believe that it is the normal direct injection rattle that everyone else here is talking about.
Enjoy the car and watch out for those POT Holes. OK maybe not in the south west.

 

Sounds perfectly normal for a 2013+ direct injection engine. I had a new dealer demo 350 loaner for a whole month before my diesel arrived, and the entire time I was wondering if perhaps they applied the wrong badges to the back. Apparenty it's the high-pressure injection system as someone else pointed out.

 

Yes - outside of the car - hood up - yes, that is the sound of high pressure direct injection - good soundproofing for the quiet cabin experience, isn't it ?

 

I have a 2013 C300, basically same engine and it's absolutely normal for direct injection engines.