Just about tried everything to get the tapping rattling to stop on my C230. This only happens when the car warms up after driving. It is perfect and quiet when you just start it. Used cleaning solvents in the gas tank. used cleaning solvents in the engine. Oil full with Mobil 1 15-40 Synthetic. Does not really increase in noise when I rev up the engine only when I let it idle you can hear it. Used stethoscope to listen and it and cant seem to locate where its coming from. Seems like injector side middle of engine but not 100% sure.. I just don't know if its ok to keep driving. Am I hurting anything by driving it like this. My next step is to maybe do the timing chain tensioner as Ive heard that can cause a noise like this. The tapping/rattleing is very faint and random. So it won't just go tap..tap.. sometimes its 1 second sometimes its 2 seconds apart. Very random. PLEASE HELP before I starting sinking more money into this beauty.