Is it safe to drive with Mercedes OM651 timing chain tensioner failure — engine rattle?

Drive with caution to the nearest garage. Avoid motorway speeds until the fault is diagnosed.

What is the most common fix for Mercedes OM651 timing chain tensioner failure — engine rattle?

Replace timing chain kit (chain, guides, tensioner)

How much does it cost to fix Mercedes OM651 timing chain tensioner failure — engine rattle?

Based on driver reports, repair costs typically range from $800 to $3500. Costs vary by make, model and location.

🟡 Mercedes OM651 timing chain tensioner failure — engine rattle

Mercedes-Benz C-Class 2010

Safe to Drive?

⚠️ Drive with Caution

Urgency Level

🔴 Fix Immediately

A rattling noise from the front of the engine on cold start that may persist until oil pressure builds. The OM651 secondary balance shaft timing chain and its plastic tensioner fail with age. The primary timing chain is rarely the cause — it is the secondary chain that causes most issues. The repair requires removal of the front timing cover and is labour intensive. Using 5W-30 fully synthetic oil and changing it every 10,000 km helps extend chain life.