How a car works

All partsBMW M4 CSLS58 engineBelt drive › Belt tensioner

Belt tensioner

Part of Belt drive · about $120 to replace

What it is

Spring-loaded arm with idler.

What it does

Keeps belt tension constant as the belt stretches.

How it fails

Bearing noise at idle.

MaterialSteel spring, plastic pulley
Spec400 N nominal
Belt tensioner highlighted on the car

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