I've only had the car awhile, but I've noticed say when parked near a wall, the resonance is very chainy, often squeaky... I've just changed the Oil with 5w-40 Fully Synthetic and the stuff that came out wasn't half bad, so I'd assume it isn't a tappet issue. There is a definately chainy noise as if the car is going to stall, despite being an automatic and the idle speed not dropping dangerously low, when on full lock and in drive or reverse (which obviously drops the revs slightly as the engine is working harder) seems to only be noticable over the hot days we've had. Been advised that it could be the shock absorber on the belt tensioner... although my M111 C200 doesn't seem to have this damper, the Belt needs changing anyway for piece of mind... So what do I need to change. Looked on ebay, there looks to be a few solid state pulleys and a automatic belt tensioner... I've looked and looked around the front of my engine bay, no damper! There's a tensioner with a torx/bolt on it which says tighten/loosen on it. Little help?