Youssef9

Hey guys,

I'm seeking some insights on a peculiar issue with my 2009 w212 equipped with the OM651 diesel engine. During warm engine restarts, particularly after the car has been stationary for around 15 to 50 minutes, I've been noticing a distinct rattling sound. While I'm not certain about the exact cause, the nature of the sound during warm starts gives me the impression that it could potentially be related to the timing chain or chain tensioner. Cold starts have exhibited this symptom only about 3 times.

But normally based on what I know the timing chain/tensionner do this sound only on cold start.

This is a video I made about that:

You Tube

I'd greatly appreciate your thoughts and experiences on whether timing chain issues could manifest primarily during warm restarts. If anyone has encountered a similar situation or has insights to share, I'd love to hear from you.Thanks for your help.

CaliBenzDriver

I am not extremely familiar with the timing gear setup of your 4-Cyl diesel. Startup does sound very much like the gasoline V6/8.

Your looking at this part list:

• VVT Phaser gear(s)
• tensioner & check valve

Once the engine timing cover is open, you'll need to manually rotate crankshaft to see if the VVT pin is worned out and lets camshafts rotate forward unlocked... You may only need the intake gear but while inside there, replace both to save labor!

The looseness during start is caused by the ultra basic chain tensioner unable to hold the chain without oil pressure. A check valve was left out on gasoline V6/8 engines (651 diesel?) that helps prevent oil drainage to built pressure faster.

I wonder if your engine features the dual-stage oil pump with a low pressure control valve - It's the one responsible for wearing out the VVT lock pin while driving, not only startup rattle.

Hearing your startup sounds, I am going to guess yes but do double-check.
You may be pleased by cancelling that low oil pressure valve... this is stil experimental and rewarding with smooth performance.