This forum has great info!
Had my 98 E320 Wagon (71k mi) for one month.
Found this forum and had the balancer and belt replaced.
$80.00 balancer, $40.00 belt, $250 (ouch!) labor.
At idle can't even tell the car is running!
When taking off no low level vibration (hum?) now.
Put the old balancer under a microscope and numerous cracks and evidence of seperation from the inside hub.
Heat, age, and torque = failure
This car is like another world compared to the 300TD (84) wagon that it replaced (which I bought used and drove for 14 years).
Again,thanks for the info!

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Feynman rules!