Aloha dear MB-World,

New to this forum and hope to find friends and knowledge ,

Happy owner of a 2015 ML550, it runs super-smoothly, it got serviced multiple times and seems in great shape.

-> The only issue is, and I went to various mechanics, and no one could locate where the sound is coming from/what it is.
-> It's not always there, but when it's there it's the "loudest" when it idles in D a bit quieter the sound when idling in N or P, in the belt/pulley area, it makes a very slight/not loud rattling noise, it's sort of quiet, but it's there.
-> One mechanic thought it was the pulley/belt.
-> Another mechanic looked at it, all belts and pulleys seem fine and firm.
-> No leakages were found.
-> Oil checks were performed all good.

Now I don't know if this is a normal sound or if I should get it checked again somewhere else, but if professionals that I have consulted (mechanics) cannot locate the issue (Mercedes Benz Service included), then that's weird. No engine lights on, it's a sound that is there if you listen really carefully.

-> Another thing, because it's a twin turbo V8, it seems when accelerating there is a slight whistle sound very soft one, when accelerating, I assume that's normal?

I would be happy to read from you and your suggestions , thanks so much!

 

The whistle is normal...turbo noise. The rattle could be your overhead cam chains (on front of engine) These have hydraulic chain tensioners that use oil pressure to tighten them up. Some early models rattled on startup before oil pressure built up (check valve was added to stop this). Might be those tensioners are bad, or chains have stretched beyond where tensioners can take up the slack.

 

Thanks a lot for this answer! Will do some more research on this and look online!

So you think there is definitely something to change/and not leave as is?

 

Hard to tell without hearing first hand. If it isnt too loud, Id prob just keep an eye on it. Maybe see if you can find another S550, CLS550 or ML550 to compare sound to.

 

Right, that is a good idea! Will ask around if someone has such a car and then listen! Really appreciated. Are you working as a mechanic ?

 

Just to confirm what Leetom has said, here a link to the chain tensioner TSP. I have a 2013 ML550 and did have this issue. It was repaired under warranty in 2014. i don't know if the new parts were put into production prior to or after that date, but your MB dealer should be able to confirm as well as review this TSP for you.
Hope this helps!
https://www.tsbsearch.com/Mercedes-B...05-10-P-056435

 

Appreciated - This forum is awesome, glad I received so far so good answers! THANKS AGAIN!

 

What I am also interested in, my ML550 sounds nice, but definitely not as strong as this:

Even if I go on Sport Mode from Comfort Mode, I do not hear such engine sounds/exhaust sounds but I have the same year and model as in the video. Why does my ML550 sound different than in the video? Thanks !

 

His exhaust was modified (per title of the video). Stock doesnt sound like this. Sport doesnt do anything to exhaust, only stiffens suspension (if you have adjustable suspension), holds gears longer in lower gears, tightens steering, and lowers ride if you have airmatic.

 

Ha! Wow, must've missed that information. I hoped to just click a button and have a smiliar sound, sounds AMAZING. Not too much, exactly right. Thanks a lot @Leetom much appreciated!!!