Steve:

Bad lifters or a bad belt tensioner shock will both make serious sounding rackets. I have a clacking lifter (only sometimes) and my brother had a bad belt shock -- rattled terribly, sounded like something bad was wrong.

You can check the belt shock by pressing it sideways with the engine running with a large screwdriver. If the noise stops while you are pushing, the gromet at the base is gone and you must replace the shock (grommet is vulcanized in place).

Bad lifters sound just like bad Chevy lifters, will be easy to locate. You can test them in place by rotating the crank and pressing down on them when they are not under pressure by a cam lobe. If you can push them down with a screwdriver, they are shot. If you have bad ones, I'd replace the lot while you have the head out (although it's rather expensive) and the theory that if some are bad, the rest will be soon. You must remove the cam.

However, you also may just have bad o-rings on the oil filter housing center "bolt" -- there are two, toward the bottom, and if they are old, rock hard, and leaking, all the oil will leak down out of the lifter gallery overnight. Causes quite a bit of lifter clack until they re-fill. You can order them or just buy an o-ring assortment and find some that fit. They do not come with a new oil filter, although I think they should. Usually last at least a couple years.

A bad chain tensioner will allow too much slack in the chain, and it will slap against the tensioner rail until oil pressure pushes the tensioner out properly. In that case, the noise will be at the front of the engine inside the chain case. Cure is a new tensioner, which I would put in as a matter or course while doing a head gasket.

Peter

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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!