Mercedes tapping noise???

[denverpete]

Clicking or ticking always sounds like valves to me - particularly with the miles stated. One thing to remember is that is that it always sounds "better" in the vehicle. You might want to get someone to rev the engine while you are outside of the vehicle - or drive it by you. If it's valves then it's entirely likely that the sound is there over a larger range then you think - you just can't hear it inside the vehicle over the sound of the engine at speed....