Serpentine Belt Replacement — DIY Guide

The serpentine belt drives your alternator, power steering pump, AC compressor, and water pump. A failed belt strands you. Replacement takes about an hour.

Symptoms

• Squealing under the hood
• Visible cracks or fraying on the belt
• Power steering loss
• Battery warning light
• AC stopped working

Tools

• Serpentine belt tool or long breaker bar
• Socket set
• Belt routing diagram (usually under the hood)

Steps

1. Photograph the current belt routing: Before removing anything, take a clear photo. There's also usually a diagram on a sticker under the hood — confirm it matches.
2. Locate the tensioner pulley: It's the spring-loaded pulley that keeps tension on the belt. It has a square hole or bolt for a wrench/tool.
3. Release the tension: Use a serpentine belt tool or long breaker bar to rotate the tensioner away from the belt. Hold it there.
4. Slip the belt off: While holding the tensioner, slide the belt off the smallest accessible pulley. Slowly release the tensioner once the belt is free.
5. Compare old and new belts: Lay them side by side. They must be the same length and same number of ribs.
6. Route the new belt: Following your photo, route the new belt around all pulleys EXCEPT the tensioner pulley. Save that for last.
7. Apply tension and seat the belt: Push the tensioner away again, slip the belt over the final pulley, and slowly release the tensioner.
8. Verify and start: Double-check that the belt sits perfectly centered on every pulley. Start the engine and watch the belt run for 10 seconds — it should track straight with no wobble.

Safety Notes

• Belt must be routed exactly per the diagram or it spins backwards
• Keep fingers clear of the tensioner — it snaps back hard if released suddenly

FAQ

How long does a serpentine belt last?

60,000-100,000 miles. Inspect annually for cracks.

Should I replace the tensioner too?

If it's noisy, leaking, or has visible play, yes. Otherwise tensioners often last the life of the vehicle.