Whatever it is, if the head comes off for a gasket replacement, by all means, spend the extra few hundred dollars to get the head rebuilt with new valve guides and valve seals. You can actually replace the seals with the head on the engine, but you can only replace seals with the head removed.

Valve guide wear is much more common on M103 engines than M104 engines, too.

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Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".