I have mistaken a noisy smog pump as valve tick, also, if you have the early version of the belt tensioner (the one with the little shock absorber) they can sometimes rattle a bit as well. Somewhere I remember reading a suggestion about adding a flat rubber washer to the top shock mount to quiet the rattle. (May have been a post by Arthur Dalton.....)

Hope this helps.

J. M. van Swaay

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1994 E320 Wagon, 230,000 miles
1995 E320 Sedan, 106,000 miles
1994 E500 Sedan, 79,000 miles