Octan3

Hi guys, 2014 e550, m278. I've noticed sometimes on a hot start the car has a... Knock or tapping noise. Not a chain rattle. And lasts about 2 seconds and it's gone. Cold starts it's never there. There is 0 chain noise or rattles. It usually takes having to sit for a hour or so hot and it'll do it sometimes. If it sits for 3 or so and has started to cool down, it doesn't seem to do it. So seems to me it's about engine being at hottest temp

I read about can adjusters but most videos I find are of a rattle noise?

Edit: found this video on YouTube. It sounds about the same, perhaps cam adjusters?
https://youtu.be/QO5TcQBOhJM?si=dApBNsjA7gXuCuGt

Thoughts? No codes either.

CaliBenzDriver

What I hear is loud but short!
-- Loud like a VVT
-- Short like a tensioner


How old are your secondary tensioners ??

Manually rotate CC to check if any of your VVT are unlocked and in particular Bank1 intake.

No ECU code is a good thing.

(VVT = Cam adjusters)
Oil pressure plays a central role in this issue.
Try to keep oil change interval shorter to preserve viscosity
Use an approved oil at least 5w40
​​​​​​

Octan3

What is CC?

As far as I know everything should be factory/ stock. It's a 2014, Looking at the chain it appears to have the updated design with the "fat" links.
the odd thing is, everybody talks about a rattle or noise on cold start, My cold start is fine, The car sat for 4 months over the winter and fired right up with out a noise, EXCEPT the typical wastegate rattle. Car only does it hot and after sitting for a bit sometimes as mentioned.

I cannot speak too much on the previous owners of this vehicle but it has 100k km on it now. I know for sure in the past 20k km It's had 3 oil changes. I just did one "just because" when I got it about 3000km ago.

S-Prihadi

CC =counter- clockwise rotation
but we must turn CW clockwise for our engine


Oh oh oh..... that is VVT sprocket rattle = $$$
Exact same as my friend's M271, but his a bit louder .

The video you linked...........

Octan3

Gotcha, yeah when I heard it I was figuring that I have a bad cam actuator that's not locking... Interesting how it only does it hot. Most people I read say cold. I'd think oil drain back but then it would do it too when cold and it never does lol.

S-Prihadi

Well by sound and duration, the knock-knock sound is not as bad as my friend's, so I guess his is mechanically worse than yours.

The engine oil pump solenoid when engine at COLD START does not activate, that gives you maximum engine oil pressure.
However, when engine is already warm/hot, the oil solenoid get triggered to purposely reduce oil pressure.
That maybe the reason during cold start you do not get the knock-knock sound
But, if your engine stay OFF for say 3 weeks, maybe knock-knock sound can happen.

Octan3

I disconnected the oil pump solenoid, I was getting the same sound at times last summer too.

That video is not mine however just found it had the same kind of tap/knock noise.

I'll try to catch the sound when I can and add it to this forum post but From what I gather It's likely somehow the camshaft actuator not locking then rattles on start up. Even when the car sat for 4 months, first start it sounded "normal" never made a noise or cam chain rattle. other than, again, wastegate rattle.

CaliBenzDriver

The part that's strange is never cold only warm. Bank1-i bad lock is specially when cold thin old oil has drained out of heads hydraulics.

S-Prihadi

Octan,

What is your oil mileage now ? Not engine mileage, the current engine oil .
How many months now ?

Octan3

I did the oil change Sept 6 2023, parked mid October for winter, then got going again a week ago. There is approx 1500km on this oil.

S-Prihadi

Well, that is basically still fresh oil.


My friend's M271.860 will make knock sound if engine kill say 3 ish hours or more, even if engine still warm

Octan3

Welp, Thus far It has not done it to me again, YAY..... If It does start to do it again I'll do what I can to get a video.

toi

My 14 sl550 with m278. Car has 78k miles.
my indy who i trust said not to worry as long as it doesnt get any longer or louder

makes this ticking noise only at warm starts after sitting sometime.

nothing at cold start

Octan3

That's the exact same sound I have too. I couldn't catch it. Doesn't happen all the time and when I think it would it doesn't.

I kinda wonder or suspect maybe the cam phasers are leaking out oil like missing one way check valves... But wonder if anybody actually knows.