It is more common than you think Matt. Basically the rubber interface breaks
down and loses it's grip making the fan belts rotate at a different speed ratio
to the crankshaft. The problem is that the timing information becomes incorrect
and the engine is impossible to re-time when it is necessary. We have several
documented instances of this and not confined to the B230F. It is a Vibration
Damper (not Harmonic balancer) fault. Harmonic Balancers are only fitted to
twin-cam engines like the B204 and B234 in the 700/900 range. Yes get it changed
asap, so that you can know how well the engine is timed, before it falls to bits
with possible expensive outcomes.

Cheers, Peter.

Yes - I agree with Peter M.  This happened on one of our 240's.
Eventually the Vibration Damper slid backwards into the timing belt
cover.  My mechanic ended up replacing that cover, as well as the timing
belt itself (it was damaged also), and cleaning out all the rubber and
plastic junk scattered in the area.

Better to take care of it sooner than I did!
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