benhogan, what's the mileage on your 1995 E320? When was the water pump changed last? As mentioned it's critical that the viscous fan clutch and auxiliary fans are working properly. If not, replacing the water pump will not resolve your overheating problem at idle.

After diagnosing the overheating problem further if you need to replace the water pump suggest buying a reconditioned water pump at your local MB dealer.

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Fred Hoelzle