There is no such thing as an unfixable car weakness

What you need to know:

  • My Toyota Vitz 2015 model has served me well in every aspect for more than a year, except I have had to change the fan belt six times. My mechanic has not found anything wrong with the system and says every vehicle comes with an unfixable weakness somewhere and that I should just keep changing the belt every now and then. I now always carry a spare. How true is my mechanic’s diagnosis? How long should a fan belt last? What could be causing the problem? What are the effects of a damaged fan belt? Kiongo

Good quality modern fan belts rarely wear out or fail if they are properly tensioned, ensuring the right size for the pulley grooves, the pulleys/tensioners themselves are spinning straight, true and freely, and the belt is not rubbing against any out-of-place projection.

If any of those requirements is at fault, all are readily fixable. A competent mechanic should be able to diagnose which of those possibilities is to blame in a few minutes.

An experienced mechanic might be able to spot the problem just by looking at the broken belt for any cuts or checking the type and position of any chaffing, and then confirm his guess by testing the groove fit and the pulley alignment and bearings.

It would be most unusual for a belt to be undergoing enough suffering to shred or snap it every few months without some other symptom that can be seen as a wobble, or heard as a screech or rattle, or smelled as burning rubber or all three. By all means ask your mechanic what he thinks the “weakness” might be, and why it cannot be “fixed”, or save yourself more time and trouble by giving him a wide berth.

Fan belts do a lot of jobs on modern cars, but most essentially, they operate the water pump. Without that, the engine will almost immediately overheat. If your fan belt breaks, you need to stop driving until it is replaced.