Mercedes 276 V6 petrol engine startup rattle

[355f]

Dear All

I have what appears to be a rattle on startup for abut 5 secoinds then all runs perfectly- no engine checklights.

Can any one suggest a speaciliast in Cambridgeshire please

[Panthro]

Is this on a C43?
I am almost sure that this will be the turbo wastegates. It's normal, nearly all of them make this noise and it does not affect the performance of the car or the turbos. My C43 did 75k with this noise. I had it checked by a Mercedes specialist and a turbo specialist and they said it was not a problem.

You can get replacement 3rd party actuators but not OEM as Mercedes don't sell the actuators separately. If you go down that route it will be a lot of work for nothing other than getting rid of the noise.

Here is a recording of my old car:

https://youtu.be/h0_vxMzGEds?si=rh76B_IuoBxb1w8x

[mwstewart]

Check the codes as there may be a pending code for cam adjustment.

[maz8062]

This is a known issue with the 276 engine. I believe it is the timing chain. Google is your friend.

[Stussy]

M276 has secondary tensioner oil feed issues, when parked the pressure/oil drains back out and causes it to rattle for a few seconds until oil pressure returns.
There is a fix to fit non return check valves in the oil feed line. Its not a recall issue and MB won't fix it for free either.
If you google, a Xentry bulletin about it can be found, I contacted a main dealer about it and pointed them to the bulletin and they literally didn't want to know. They wouldn't even show any interest to sort it if I paid either!

In the bulletin it states no damage can be caused and its just a noise.
Mine has rattled for about 4 years now, I've asked various supposed Mercedes specialists and not a single one seemed to want the work, which seemed odd to me!