If you’re a proud owner or prospective buyer of a 2007 Mercedes Benz Sl550, it’s crucial to be aware of a potential engine issue affecting models from this era. Specifically, certain Mercedes-Benz vehicles equipped with the M272 V6 and M273 V8 engines, including the SL550, manufactured up to mid-2007, may be susceptible to premature wear of the timing chain sprocket.
This issue stems from a manufacturing defect in the heat treatment process of the sprocket, making it softer and less durable than intended. In V6 engines, this sprocket is integrated into the balance shaft, while in the V8 SL550, it’s a separate idler sprocket. The problem manifests as wear on this sprocket, leading to slack in the timing chain.
Understanding the Problem:
In the Mercedes Benz SL550’s M273 V8 engine, the worn idler sprocket disrupts the timing chain’s geometry. As the crankshaft pulls the chain, the wear on the sprocket effectively shortens the distance between it and the right camshaft. This causes the right camshaft to become “retarded,” meaning it lags behind the crankshaft’s intended timing.
Symptoms of a Worn Sprocket:
Initially, the symptoms might be subtle and intermittent. You might experience:
- Chain Rattle: A noticeable rattling sound, particularly on startup.
- Intermittent Error Codes: Specifically, trouble codes 1200 and 1208, related to camshaft position, may appear sporadically.
As the sprocket wears further, these symptoms become more pronounced and consistent:
- Persistent Error Codes: The 1200 and 1208 error codes will appear as “CURRENT” immediately upon starting the engine.
The engine’s variable valve timing system can initially compensate for minor timing discrepancies. However, prolonged wear can lead to more serious issues, including:
- Timing Chain Damage: Slack and scraping against the worn sprocket can damage the timing chain itself.
- Internal Engine Damage: In rare cases, fragments from the worn sprocket could circulate within the engine, potentially causing further internal damage.
Affected Models and Identifying Potentially Problematic Engines:
This issue primarily affects Mercedes-Benz models with M272 V6 and M273 V8 engines produced up to mid-2007. These engines were widely used across the Mercedes-Benz range, starting from the 2005 SLK350 and becoming prevalent in most non-AMG V6 and V8 models through approximately 2011. The manufacturing flaw was corrected around mid-2007 production year.
To determine if a 2007 Mercedes Benz SL550 (or other affected model year) falls within the potentially problematic range, you need to check the engine serial number. This number can be found on the data card (build sheet), obtainable using the Vehicle Identification Number (VIN). A helpful online resource for this is a VIN decoder for Mercedes-Benz.
Key Engine Serial Numbers to Check:
- For V6 engines (M272): If the engine serial number is 30 468993 or earlier, it is within the potentially affected range.
- For V8 engines (M273), like the SL550: If the engine serial number is 30 088611 or earlier, it is within the potentially affected range.
Engines with serial numbers after these figures are considered to be outside the problematic production window.
Advice for Owners and Buyers:
If you own a 2007 Mercedes Benz SL550 or are considering purchasing one, especially within the affected model year range, it’s prudent to:
- Check the Engine Serial Number: Utilize a VIN decoder to obtain the data card and locate the engine serial number. Compare it against the critical numbers provided above.
- Pre-Purchase Inspection: If buying a potentially affected vehicle, have a pre-purchase inspection performed by a qualified Mercedes-Benz mechanic. They can check for symptoms of timing chain wear and potentially assess the sprocket condition.
- Repair History: Inquire about the vehicle’s service history. Has the balance shaft or timing chain sprocket been replaced? If so, request documentation of the repair.
While not every engine within the affected serial number range will necessarily fail prematurely, the risk is elevated. Being informed and proactive is the best approach to ensure the longevity and reliability of your 2007 Mercedes Benz SL550.
