The tick could be lifter noise or injector knock (#4 clacks pretty bad at idle on my 87 300D) -- one cause of lifter noise is dead o-rings on the center bolt on the oil filter cap. They aren't in the filter box, so no one replaces them and the oil leaks down from the lifter gallery overnight, takes forever to pump back up.

Head gaskets are a problem, too -- and I get the feeling that a bad one can cause low compression on some cylinders, causing injector knock.

Mine is supposedly low on compression, especially #4, leaking down the rings, but I don't have any oil consumption, it gets 36 mpg on the highway, and no smoke.

I do have a brand new rad and some black oil collecting in the coolant tank, though ---- suspect I'll be doing a head gasket soon!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!