iamkimosabi

Car: 2012 C350 BlueEfficiency V6 3.5 302 hp
Miles: 37K
Transmission: Automatic
Issue: Car starts with 3-5 seconds of chattering / clacking noise

I've searched, but couldn't find a definite answer to this or in most cases i've read problems that were similar to mine but the sound is constant, mine is only during engine start. I have a rapid clack clack clack clack clack sound on engine start up. Some of the things i have read are that it is due to direct injection. Some others I have read say its the timing chain tensioner. Some say its the cam tapping, some say hydrolic lifters, some say it's a valve pin. The noise is exactly like this


Too bad I don't speak this language

iamkimosabi

So here’s an update, I measured the oil and found it to be full past the red plastic on the dipstick. Emptied out a little bit till the dipstick showed oil in the center. Made sure oil filter was correct, drove it around for 70 miles for two days. Tried to replicate the sound to record on video but now it won’t make the sound. Took it to the benz dealership in Georgetown Texas today and they couldn’t hear the noise...and they wanted me to drop it off Tuesday and leave it over night, so they can try cold starting in the morning.

Could it be the dealership I bought it from over filled by mistake and that made the chatter? Or the battery is going out so the starter isn’t getting enough juice, making a clack clack sosubd?

superangrypenguin

They typically overfill. That said I swear to God my car has a mind of its own. After an oil change I start up the car, then turn it off, fill it to the full mark, and a 50km drive after I'm overfilled. I correct it and then the issue is resolved until the next oil change. Wtf?

iamkimosabi

Weird, well i havent had the noise come back, and im scared to take it to the dealership. Something about paying 1 thousand american dollars for each cam adjuster, and he said 4 of them, and not including the chain tensioners, and check valves....and labor.....i might just take the car back if it comes to them having to do all that to the engine, or even worse....having to get it rebuilt due to the damage already. i have no check engine lights, no rough idle, drives great, no noises besides the initial start up vroom...idk. idk what to do...i just dont know.

if it looks good, sounds good, runs good, and drives good....is it good?

dol4er

If the sound was gone, I would just wait. Although I doubt an overfill could cause such a sound... once I had overfilled because of my stupidity and it didn't make any sound.

iamkimosabi

The dealership said the car was sitting for 50 days...low battery messing with the starter making a grinding noise after the car starts, for 2 seconds perhaps?

Tom in Austin

There was a problem with early M276s where oil somewhere in the valvetrain would leak down after the car sits, leading to a rattling sound at start up. I believe there is an improved valve that can be fitted to fix this but the service bulletin I saw said this condition would not result in any harm to the engine, just disconcerting noises.

W204Motorsports

Sounds like oil isn't getting somewhere it needs to, I believe there was a bulletin with this issue on the m276 engine.

alecmascot

" Problems

Basically they are very good engines although some had issues with rattling or noisy timing chains on start up. The issue is to do with oil not get to the chain quickly enough and was addressed by Mercedes in the attached bulletin that tells you everything that you need to know.


The engines affected are :

Engine 157:

1) From engine number 157 9xx 60 009368 up to engine number 157 9xx 60 017984 install check valves and chain
tensioners

2) From engine number 157 9xx 60 017985 up to engine number 157 9xx 60 022333 (December 2012) install check
valves (optimized tensioners installed in this production range)
08-12-2013 1:44 AM d7recast

Engine 2768:

1) Up to engine number 276 8xx 30 000790 install check valves and chain tensioners

2) From engine number 276 8xx 30 000791 up to engine number 276 8xx 30 001281 install check valves only
Engine 2769:
1) Up to engine number 276 9xx 30 365996 install check valves and chain tensioners
2) From engine number 276 9xx 30 365997 up to engine number 276 9xx 30 406603 (February 2013) install check
valves only (optimized tensioners installed in this production range)
Engine 278:
1) Up to engine number 278 9xx 30 073273 install check valves and chain tensioners
2) From engine number 278 9xx 30 073274 up to engine number 278 9xx 30 103675 (February 2013) install check
valves only (optimized tensioners installed in this production range)
Note:
When performing repairs and only the check valves are supposed to be installed, the tensioners must still be checked
according to WIS documentation. If optimized tensioner is found to be defective it must be replaced "

From mbclub.co.uk

iamkimosabi