Timing Chain Bulletin
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




There is an old post about this: Making a weird noise on startup. Please help!
Normally Service Bulletins are not covered after the warranty expires but you can always just go talk to them about it and see what they say

Here is a YouTube video showing how it is done:
Here is .PDF file copy of the service bulletin itself:
Last edited by JRHolt; Apr 17, 2018 at 12:52 PM.







