Originally Posted by iminhell
I have covered this before.
There are 3 types of pulleys in automotive use, a pulley, a dampener and a balancer. Each has a specific purpose.
A pulley is simply there for a belt to ride on and rotate.
A balancer is used to help balance some component. It offsets torsional flex in an internal shaft generally.
A dampener is used to absorb, limit or isolate harmonic vibration from one component to another.
The zetec has a harmonic dampener.
I agree, if it wasn't then it wouldn't be so heavy in the first place. It would just be a stamped steel pulley or something. It's just there to dampen the vibes so the normal folks won't complain when getting groceries.