Balance Shaft Gear Failure (M272/M273)
The M272 V6 and M273 V8 engines produced between 2004 and 2008 suffer from a well-documented idler gear failure in the balance shaft assembly. Mercedes used a soft, sintered-metal compound gear that wears prematurely, causing timing chain slack and eventually catastrophic engine damage if not addressed.
Which models are at risk.
Warning signs to watch for.
Check engine light with P0016, P0017, P0018, or P0019 camshaft-to-crankshaft correlation codes
Rough idle, especially when cold
Rattling or chattering noise from the front of the engine on startup
Loss of power or hesitation under acceleration
Engine misfires at low RPM
Timing chain rattle that worsens over time
Why this happens.
Soft sintered-metal compound used in the idler gear wears prematurely
Early production engines (2004-2008) used a gear material that was not durable enough for the loads involved
The balance shaft gear meshes with a steel sprocket, causing accelerated wear on the softer gear
Inadequate oil change intervals accelerate wear due to metal particle contamination
Mercedes issued a revised steel gear (part supersession) for later production engines
How we diagnose it.
- 01
Read fault codes with Star Diagnostic — look for P0016 through P0019 camshaft/crankshaft correlation codes
- 02
Check camshaft and crankshaft position sensor waveforms with an oscilloscope to measure timing deviation
- 03
Perform a relative compression test to rule out mechanical engine damage
- 04
Remove the oil pan and inspect the balance shaft gear for wear and metal shavings
- 05
Measure timing chain elongation with the Star Diagnostic timing chain measurement routine
- 06
Check engine serial number — engines produced before approximately June 2008 are most at risk
How we fix it.
Replace balance shaft gear and timing chain with updated steel components
Correct repair with updated parts; addresses the root cause; full engine timing restoration
Labor-intensive (15-20 hours); requires engine removal or significant disassembly on some models
Complete engine replacement with a later-production M272/M273
New or remanufactured engine with revised gear; fresh wear items; warranty on replacement
Higher cost; sourcing a quality replacement engine requires verification of production date
Used engine from later production (post-2008 revision)
Less expensive than new; later engines have the updated gear from factory
Unknown history of used engine; may need additional wear items replaced during installation
Keep it from happening.
Change engine oil every 7,500 miles or sooner using MB 229.51 specification oil
Use only quality oil filters that trap fine metal particles (genuine Mercedes or MANN/Mahle OE-equivalent)
Listen for any new engine noises on cold start and address promptly
If buying a used M272/M273 vehicle, verify the engine serial number to determine if it has the updated gear
Consider proactive replacement of the balance shaft gear on pre-2008 engines before failure occurs
Common questions.
How do I know if my M272 engine has the updated balance shaft gear?
Mercedes revised the balance shaft gear to a harder steel compound around mid-2008. You can verify by checking the engine serial number — engines with serial numbers after approximately 2729xx (M272) and 2739xx (M273) typically have the updated gear. Alternatively, removing the oil pan allows visual inspection of the gear material and condition.
Can I drive with a worn balance shaft gear?
We strongly advise against it. A worn balance shaft gear allows the timing chain to develop slack, which progressively worsens camshaft timing. Continued driving can result in the timing chain skipping teeth, causing valve-to-piston contact and catastrophic engine damage. What starts as a $4,000 gear replacement can become a $10,000+ engine replacement if ignored.
Was there a recall for the balance shaft gear issue?
Mercedes-Benz did not issue a formal recall but did extend warranty coverage on some affected vehicles and issued a Technical Service Bulletin (TSB). Some owners successfully obtained goodwill coverage from Mercedes-Benz. The class-action settlement (Berman v. Mercedes-Benz USA) provided partial reimbursement for some owners, but the settlement period has closed.
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Learn more →Let’s take care of your Mercedes.
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