If it's truly leaking between the head and block, the head gasket needs to be replaced. The head gasket is thin in that area and is prone to going bad. It's a common problem for your engine.

The head bolts are torque-to-yield bolts. Thightening them up won't do. During installation they're tightened to a certain torque, then a 90° turn and another 90° turn.

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95 E320 Cabriolet, 169K