How To Replace Serpentine Idler Pulley 99-07 GMC Sierra
Difficulty: Intermediate · About 90 min · Gmc Sierra
Replace the serpentine-belt idler pulley on a 1999–2007 GMC Sierra, noting the belt routing before removal and checking that the replacement pulley spins smoothly and the belt tracks correctly.
Tools you will need
- 15mm Socket
- Torque Wrench
- Ratchet
- Flat Blade Screwdriver
Parts and supplies
- Serpentine-belt idler pulley
Steps
- Move the intake hose for access
Loosen the air-intake clamps and release the radiator-hose clip from the intake duct. Separate the hose from the throttle body and move it aside without stressing the connected breather lines.
- Remove the serpentine belt
Review the under-hood belt diagram and note the belt path. Turn the tensioner with a 15 mm socket to relieve tension, slip the belt off, and release the tensioner slowly.
- Replace the idler pulley
Remove the pulley bolt and lift off the old idler. Transfer its spacer to the replacement pulley, position the new assembly, and tighten the bolt to the vehicle specification.
- Route and inspect the serpentine belt
Follow the routing diagram to place the belt around each pulley, keeping ribs aligned with grooves. Relieve the tensioner to fit the final section, release it gradually, and check that every rib sits correctly.
- Reinstall the intake hose
Return the intake hose to the throttle body and tighten its clamps. Reattach the radiator-hose clip and verify that no hose or wiring can contact the moving belt.
Check your vehicle’s repair manual for exact specifications and fit.