Another thing to consider doing is to replace the lifters. My '88 300TE had one or two that were intermittently making noise (indicating that they were leaking down) so I replaced them. I just did the entire deal at 165k (head gasket had begun to weep a little oil out the back of the motor, and there was a tiny bit of oil in my coolant expansion tank), so I'm speaking from recent experience. And assuredly do the valve job while the head's off!

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"If God had meant for us to walk, why did he give us feet that fit car pedals?" Sir Sterling Moss

Michael
2014 E63S Estate
2006 SLK55
1995 E500
1986 Porsche 944 turbo