Yes its a different thing, however if the pulley has to come off for any reason, timing belt replacement for example, the bolt must be renewed...In your case though, if the pulley has become damaged or started to seperate and wobble, it can put undue loads on the bolt, thereby causing it to fail anyway.

Its a strange problem really, sometimes appearing after work involving the timing belt. Could be the reuse of the bolt, or an innapropriate way of removing the pulley causing damage to it. There is of course a known problem with the pulley but early replacement will sort it. There was a similar problem with the 4cyl 1.1 I think aswell.

The pulley and sprocket are both keyed to one another and the to crank so balance 'shouldnt' be an issue, if a new pulley is used it must be a genuine piece which will be correctly balanced of course.

A Kia or Hyundai dealer is the best person to ask about this problem though, especially if it is still under 7 year warranty.

Edited by countryroads on 28/12/2012 at 17:53

Should have said "Wish"