IMHO, you cannot "check" the balancer with any degree of confidence. I had the balancer on my E430 changed in October of 2002 (my dealer changed it under warranty before it failed). At the same time, I advised my 87 year old mother (in California), who drives a '99 C280, and still runs a business some 100 miles from her home, to inform her dealer of the problem and to have hers changed out even if she had to pay for it. When she took the car to the dealer in December 2002, they advised her that they had not seen much of a problem with these and would not change it, even if she paid. They told her they would "keep an eye on it" and in fact, it was checked in June of 2003. Last Thursday (August 28, 2003) the balancer flew apart. It went with no warning - no noise, squealing, or vibration. The car had to be towed 45 miles to the dealer. The dealer "goodwilled" the repair, which fortunately involved only replacing the balancer and belt - the timing cover and pan were not damaged. During my discussions with the Service Director, he admitted that checking the balancers is not reliable. So, get yours changed. In the overall scheme of things, it is a cheap fix.