Tried this. No effect, as far as I can see, though my symptoms are different. Anyway, the car is in for a service today. I'll see what they say. (I gave them an overall budget, and there are a couple of other items that need fixing too.)

Momo

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1990 500SL 65k km - until May 11 2004
2004 E320 4-Matic wagon
2004 CLK500 Cabrio from May 11 2004