We may have a winner here. We had just finished replacing the upper radiator hoses, thermostat, and belt a few days before this all started. The tensioner gave us fits when we reassembled, but we thought we got it "fixed." Thinking back, the wife did complain that the belt was squealing some, and we were going to look at that before this "tapping" started. We have concentrated on the tapping since then and not even looked at the belt or tensioner....

...until last night that is. Sure enough, the belt tensioner isn't working. We were able to move it back and forth and make a tapping sound by hand, so at 1000rpm......well, you get the idea.

Parts on their way to completely replace the tensioner assembly and all peripheral parts. Hope this is it. More to come.....

__________________
Andy_M
'98 W140 S320 Black/Black
'06 W164 ML500 AMG White/Grey
'03 Porsche 986 Midnight Blue/Grey

Andy, I guess you know not to tighten the center bolt on the tensioner until after the belt tension is adjusted properly. Otherwise, you will destroy the tensioner. Also, be sure the tensioning adjustment rod is on the side toward the engine when positioning it on the the new tensioner assembly.

__________________
Fred Hoelzle

Nice call on the tensioner shock!

Well, she has a nice new tensioner assembly on her now (which she needed anyway,) and the oil has been changed to the recommended 10W-40 .....

......and the ticking hasn't gone anywhere. Still comes and goes, still "moves around." HAS to be lifters, but I am still bugged about how "all of the sudden" I have multiple lifters failing to pump up and stay pumped up.

Going to try one last thing before I order a whole new set of lifters, I'll run a bottle of Gunk engine cleaner through, then change the oil again. I'll try the Rotella if I can get it around here. More to come.....

__________________
Andy_M
'98 W140 S320 Black/Black
'06 W164 ML500 AMG White/Grey
'03 Porsche 986 Midnight Blue/Grey

Awwww man!!! Only other thing I'm thinking is that could it be an arcing noise from a plug wire or two? I caught mine one day just by luck looking at the engine at night in the dark!

Well fellas, sometimes all you need is a bottle of engine cleaner and 10 mins of time........

Started her up and put in a bottle of Gunk Engine Flush. Can says put it in a cold engine and let run for 5 mins. I put it in a cold engine and let her run for about 10 mins.....wanted to give it every chance to tap. Twice I heard it j-u-s-t s-t-a-r-t to tap a little and stop right away. Then I heard no more offers to tap. Shut her down and changed the oil....Castrol Syntec 10w-40, and been running it around for two days now without a hitch (or a tap). Mind you....the inside of the engine looked beautiful to start with. Would not have even thought I needed to flush it.

It is also running smooth as silk....much smoother than before all this. Not sure if the new distributor cap and rotor I put on while I had all this apart anyway did that, or if the engine flush did.

FINAL UPDATE: A week later and it is still fine so I guess the engine flush did the trick.

__________________
Andy_M
'98 W140 S320 Black/Black
'06 W164 ML500 AMG White/Grey
'03 Porsche 986 Midnight Blue/Grey