Engine
Accessory Belt
The serpentine belt drives the alternator, water pump, power steering and AC compressor.
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Combustion flow
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What it does
- Transmits engine power to accessories
- Ribbed for grip on multi-groove pulleys
- Auto-tensioners keep it tight
When it fails
- Squealing on cold start or when loaded
- Cracked, glazed or frayed belt
- Loss of power steering or charging
- Belt shredded after a seized pulley
How to diagnose
- Inspect the belt for cracks and wear
- Check the tensioner and idler bearings
- Spin each accessory pulley by hand
Maintenance
- Replace the belt and tensioner on schedule
- Replace seized alternators, compressors or pumps quickly
Use the diagnosis order. When a part fails, confirm each hypothesis with measurements before replacing anything — codes and symptoms overlap.
Related part
Alternator
The alternator converts mechanical engine power into electrical power to run the car and recharge the battery.