Originally Posted by NeedsWings
just got this back...
do we need cores?
"no they do not. Normally we would accept cores but on
part numbers 331380 & 331390, Mercedes has had problems
with the stock units so in order to avoid any problems we
supply a new balancer rather than possibly taking in a bad
core."
That problem comes from the rubber dampener in the crank pulley. It is a possible problem even with the ASP pulley because the ASP pulley is just a modified MB factory pulley. Problem is the rubber Dampener in the pulley can dry rot from hot and cold cycles and may fall out causing a engine misfire code and engine shut down. Just so you know this is very rare but that is the reason they only use new MB pulleys.