BenzWay

My e400 2016 I bought recently with 40k miles has developed this knocking sound at idle. It usually happens when I push the car in sport mode and stop at a red light. It’s a consistent knocking sound that only happens at operating temp at idle in drive and never when the cars cold. I am using only shell v power 93 octane so I’m guessing it might have something to do with the spark plugs but am not too sure and need some help.

ygmn

Search waste gate... I think some have complained about it making noise.

S-Prihadi

Which country are you located at ? When you speak of octane a 93 oustide USA, say in Europe and Asia ( I don't know Canada ) it is RON 93 and our E400 at least for my country version need RON 95 but I use RON 98.
USA octane is AKI, its actually higher.

If you are in USA, then it should be fine using octane 93.

BenzWay

yeah I have that wastegate noise when I accelerate under load but this knocking just sounds like something completely different it only happens at idle too, I don’t think the wastegate would make a knocking noise at idle

BenzWay

yeah that’s why I’m assuming it could be a spark plug issue maybe the previous owner put aftermarket plugs in which is causing the knocking/pinging ughhh

BenzWay

The car itself runs perfect though no engine hesitation and I do occasionally see white smoke from exhaust while I’m at a red light and the coolant isn’t leaking whatsoever so I’m guessing maybe emission related thing, fuel pump, spark plug causing the knocking? I doubt a lifter or rod would go bad on a Mercedes and I got a recent oil change using 5w40 molly which didn’t make a difference in the knocking. I’m also starting to think maybe loose heat shield

S-Prihadi

If you want to test for iginition knocking, use manual gear mode , set to highest gear, keep it as low RPM as possible and full throttle......... ignition knock is more obvious if pushed this way

BenzWay

I tried that and nothing really sounded out of the normal, I heard from another forum that the dealer said this noise is due to loose wastegate for the turbos. It’s weird because the noise comes and goes during every fillup. These past few days I have been also seeing excessive exhaust smoke compared to other cars at idle during freezing temperatures. I guess the trip to the dealer is coming sooner than I thought

atraudes

If you're only seeing steam coming from your exhaust when it's cold out and everyone's car is doing it, I wouldn't worry about it. Some cars kick out steam like a stadium fog machine, and others don't. It can even vary on an individual basis. However, if you're seeing steam consistently, then you have something like a coolant leak.

That said, the knock is worrisome. Definitely get it addressed. Good luck!

BenzWay

Will do, I’m dropping the car off this Friday at the dealer and hopefully a fix comes up. Also I’m not losing any coolant so hopefully I’m just over reacting over the smoke

SteveE400

If the knock happens at idle, I would probably rule out anything to do with spark knock (pre-ignition), as this only happens when the engine is under load. At idle, it can't be under load, so your noise must be something else.

Also, if it was the plugs, I would expect CIL or error codes to show up. Yes, it could be a physically damaged plug, coil, or other ignition part which is really arcing to ground - but again, I would expect an error or fault code.

You should still be under factory warranty, so I would let the dealer deal with it.

ObanSkye

I’ve got the same issue. Rhythmic clacking that goes away with engine revving. Not noticeable until after engine warmup but only then at idle. Seems to have become more pronounced with car being used less due to working from home. Definitely not related to engine knock. Definitely not transmission related. Almost sounds like metal or a belt contacting a plastic cover. Did anyone definitively figure this out? I pointed it out at last service and of course the dealer didn’t hear it and said all was normal.

BenzWay

The dealer said it was normal and since then I’ve been driving the car normally with no issues. I would assume maybe a loose heat shield tapping the engine?

ObanSkye

The sound is definitely not normal which irritates me. It is laziness on my part and the dealership not to get to root cause. The question is who wants to pay until the issue is found. I just need to know what if it is serious like a timing chain loose or minor like a cover flapping. I just wish that when you pay $200 for an A service (glorified oil change and checklist) and you report the noise that you get a highly trained service tech to address the problem in writing and document it. By denying the noise itself or calling it normal which we all know it isn’t (otherwise why would we post here) for a vehicle under warranty you just have to wonder if we are all going to get a larger bill later because we’ve ignored a noise that could have been corrected earlier and under warranty.

YasS

I hear that at cold start. It's like a metal clanking.

Also, does the E400 sedan have a fake engine noise? It seems like it does when the music is low or off?

oldmots

I have read that there have been some issues with cam chain tensioners in these cars, so you will need to have it looked at. More than one tensioner has been replaced to solve this issue. At idle, the hydraulic tensioners react to the lower oil pressure by reducing the tension on the chain. If the tensioner is leaking, it can release too much pressure and the chain will rattle.

konigstiger

Applicable bulletins released by MBUSA, see attachments.

MBNUT1

https://mbworld.org/forums/sl-class-...y-startup.html

badbenz94

My engine falls in that segment for improved tensioners...is there a way to see if it has been done without going to the dealership? Dont want to set off alarms...but my car came with a 90 day/4k mile warranty and would like that "fixed" if I can under warranty.

Thanks!

Chris

juanmor40

Without physical evidence, say opening the timing covers, the only thing would be to have access to your car VMI at an MB stealership. The latter assumes the service records are up to date.

Do you already have a reputable/trustworthy Indy in mind for future service?

badbenz94

Thank you. Yes I have a place that used to service my old 94 on things I wasn’t comfortable doing back then. Im pretty sure they could get it fixed. It’s a $200 deductible but it’s worth it I think.

Chris

S-Prihadi

DELETED

Spades

As much as everyone hates reviving an age old thread .. I didn't want to start a new one. Did anyone ever find a solution to this? My '16 E400 has now started doing this and it's driving me crazy. Love the car .. hate the knock at idle. On our dinner date last night that wife started commenting on it so I started searching today and found this thread.

CaliBenzDriver

How do you like the TSB knowledge by @konigstiger under post #17 ?

Spades

Except none of those are the knocking sound at idle that has been described in detail in many threads .. thank you though.