When turning your fan by hand, are your belts supposed to turn too, or slide across the pulley?

  • 7
    Welcome to mechanics.se. Unfortunately, I don't understand this question. What does "r" mean? Can you explain in more detail what you are doing and why, what happens, and what you expected? Standard spelling and complete sentences also help. You can use the "edit" button to make changes. Jan 7, 2015 at 21:12

1 Answer 1


The belt should turn too if they are tight enough, sliding tells that the pulley is worn down or the belt is not tight enough/is also worn down. The fan pulley also includes the waterpump which will provide resistance at higher speeds so it should not slip at all.

  • 1
    They'll have to slip somewhere - either the fan pulley or the crank one...
    – Nick C
    Jan 8, 2015 at 13:23
  • Why would they have to slip? Slipping is what destroys the rest of the belt very fast so that is an absolute no-no.
    – Elias
    Jan 8, 2015 at 13:26
  • 2
    If you can turn the fan by hand without the engine turning, then something has to give, as the fan and crank pulleys will be turning at different speeds... It'll be whichever of the two has less friction with the belt. And yes, it is bad for the belt!
    – Nick C
    Jan 8, 2015 at 13:28
  • Ah now I get what you mean, indeed if the engine is not being turned at the same time the belt would have to slip somewhere. Apologies for the confusion.
    – Elias
    Jan 8, 2015 at 13:35
  • Whoever downvoted my reply can also then tell what is wrong with the reply.
    – Elias
    Jan 9, 2015 at 14:16

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .