When the chain skips, major engine damage can occur if the valve timing goes out of sync far enough for the valves to hit the pistons.įor some reason, Mercedes-Benz decided to use a single row timing chain in the M271 engine while its predecessors, the M111 and the even older M102, had double row timing chains, which were very reliable. I believe this is why most of the M271 failures occur during engine start up. What happens is that when the chain is stretched too much, the spring alone cannot apply enough tension, and it becomes possible for the loose chain to jump some teeth on the timing gears. There is also a spring that applies some tensions when the engine is off and there is no oil pressure. The tensioner uses oil pressure to apply tension to the chain when the car is running. As the chain stretches, at some point it will reach the limit of what the chain tensioner can compensate for. There have been cases of premature chain stretch in these engines. Leaving it for this long in the M271 engine is very risky, in my opinion. Generally, when a timing chain is used, the intention is for it to last the “lifetime” of the engine (very roughly 200k miles). how the metal core is joined with the plastic sides. You can identify a Valeo radiator by the crimping method i.e. Only cars manufactured before 09.2003 are affected and newer Valeo radiators are fine. It’s much cheaper to replace a radiator as a precaution than it is to replace a dead transmission. If you do buy a car with a Valeo radiator, consider having it replaced as there is still a small risk that it could fail. The majority of the C-Class vehicles on the road today would have had the faulty radiators replaced by now. Definitely look out for this when test driving a W203 C-class made before 09.2003. The typical symptoms of a failing radiator seal are harsh gear changes and humming/droning noise during light acceleration up to 2500 RPM. If the contamination was stopped quickly enough, a transmission flush and new transmission fluid may be enough (not that expensive) Rebuild the transmission (also expensive) The fix for a transmission contaminated with coolant is to: The coolant in the transmission is not a good thing and causes severe clutch surface wear, among other issues. Cars with manual transmissions are not affected. This oil/coolant mixture can ruin the transmission if not flushed quickly. The faulty radiators were made by Valeo and had a problem with an internal seal that was supposed to separate the coolant from the transmission oil.Ī failed seal would release the coolant into the transmission oil circuit. The transmission oil cooler in these cars is integrated with the radiator. The early W203 models, manufactured before 09.2003, might have been fitted with radiators that can cause expensive automatic transmission failures.
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