Q&A

 Master

The ticking at idle is most likely the hydraulic lifters. Dirt and carbon will clog the little valves inside of the lifters so that they don't maintain the proper clearance and therefore will tick. You should always use a high grade synthetic oil ( Mobil I 5w-40 European ) and change it every 4-5000 miles. The automatic oil change system is kind of suspect.

the ticking is very likely the lifter oil feed tubes. these are little 1 " long plastic tubes that feed the oil to the lifter. they are on top of the head under the valve cover and are held in place by the the cam bearing cap. can be changed one at a time without removing the cams. The problem is there is a little plug in one end of the tube, it is only glued in place. it gets loose and allows oil to bypass the lifter casuing the loud tick. if the cap came off completely it always ticks but if its just working its way out, it may tick then stop and back again. the tick it loud. if the cap fell out compeltely you probably will never find it, its gotten chewed up and gone. its Ok its only plastic. MB calls them cam lube tubes, $15.50 each and there are 16 of them. you can do what i did just replace the bad one, but they seem to have about the same lifetime cause i had to go back in twice to replace other ones. just replace them all. most of the work is getting at them having to remove the valve covers so just replce them all.