Why does the Mercedes-Benz 272 engine make abnormal noises when hot?
2 Answers
Mercedes-Benz 272 engine makes abnormal noises when hot for the following reasons: 1. Cold start noise. The oil pump has not yet fully built up oil pressure during cold start, resulting in insufficient lubrication for various components. Normally, the abnormal noise will disappear after the engine runs for a while. 2. Aging or loosening of engine mounts. The function of engine mounts is to reduce vibration and cushion the engine's operation, as well as to fix the engine. Once these mounts age or loosen, the engine will vibrate, and in severe cases, abnormal noises will occur. Simply replace with new engine mounts. 3. Overly rich air-fuel mixture. When the engine's air-fuel mixture is too rich, acceleration becomes difficult after starting, the engine runs unevenly, the exhaust pipe emits black smoke, and the engine is accompanied by a rattling noise, sometimes backfiring; engine power decreases, fuel consumption increases, which is related to carbon deposits, clogged filters, etc.
I've driven a Mercedes for several years, and the abnormal noise from the 272 engine when it's hot is likely related to the timing chain. As the engine oil heats up and becomes thinner, the chain tensioner can't maintain proper tension, leading to a rattling sound. Another possibility is aging of the water pump bearings, which produces more friction noise when hot, sounding like metal scraping. This issue needs to be addressed early. I once delayed and the chain loosened, nearly damaging the engine. After replacing the tensioner, it became quiet again. Regular oil changes and water pump inspections are crucial—don't wait until a major repair is needed. This problem is common in V6 engines. My advice is to pay attention to any changes in engine noise and get it checked by a professional shop immediately if anything sounds off. Hot engine conditions are when problems are most noticeable—don't compromise safety to save money.
