Idler & tensioner replacement
Idlers and tensioners maintain the belt’s correct tension and running path.
Symptoms
- A hum at idle that changes when the AC switches on, or squealing right after startup.
What's included
- Their bearings wear gradually; the first signs are humming at idle that changes when A/C is switched on, or squealing after startup. A seized pulley is dangerous: the belt immediately breaks or comes off, and in a timing drive this allows valves to hit pistons. We check every pulley for play and free rotation with the belt removed, since the defect is often inaudible with the engine running. We replace pulleys together with the belt because they are designed for the same service interval, and control tightening torques.
Additional checks
- Play and free rotation of each pulley — checked with the belt removed
- Tightening torques — controlled during installation
Why it matters
A seized roller is dangerous: the belt snaps or flies off instantly, and on timing belts that ends with valves meeting pistons. It's replaced together with the belt.
More details
Idler and tensioner pulleys keep the belt properly tensioned and guide its path. Their bearings wear out gradually, and the first sign is a hum at idle that changes when the A/C is switched on, or a squeal after startup. A seized pulley is dangerous: the belt snaps or comes off instantly, and on a timing belt this ends with the valves meeting the pistons. We check every pulley for play and smooth rotation with the belt removed — on a running engine the fault is often inaudible. We replace the pulleys as a set with the belt, because their service life is rated for the same interval, and we check the tightening torques.
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