Drive Belts
The drive belt, also called the auxiliary or serpentine belt, transfers power from the crankshaft to the alternator, water pump, power steering pump and air conditioning compressor.
What it does
A single ribbed belt routed around several pulleys, held at correct tension by a spring-loaded or manually adjusted tensioner.
Signs a drive belt is failing
- A squeal on start-up or when steering at full lock
- Visible cracking, glazing or missing ribs
- The battery warning light, if the belt is slipping on the alternator
- Overheating, if the belt drives the water pump
- A chirping that follows engine speed
When to replace them
Inspect at every service and replace at manufacturer intervals or on visible cracking. It is inexpensive relative to what it drives.
What to confirm before ordering
Have these ready and the counter can usually confirm the part in under a minute.
- Engine code and whether the vehicle has air conditioning, which changes belt length
- Number of ribs and overall length
- Whether the tensioner and idler pulleys should be replaced at the same time
Drive Belts questions
What happens if the drive belt breaks?
You lose everything it drives at once: charging, power steering assistance and, on many engines, the water pump. If the water pump is belt-driven the engine will overheat within minutes, so stop rather than continue.
Should the tensioner be replaced with the belt?
It is strongly advised. A weak tensioner lets a new belt slip and squeal, and the labour to reach it is already spent while the belt is off.