Technical Service Bulletins

Diagnosing belt noise with laser tool

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Diagnosing belt noise with laser tool

GM notes that their tool program now offers a competitive and simple-to-use laser tool to assist in achieving precise alignment of the serpentine-belt drive belt pulleys. The Kent-Moore EN-49228 Laser Alignment Tool removes the guesswork from proper pulley alignment, eliminating complaints of drive belt noise, accelerated belt wear and drive belt slippage.

CAUTION: Do not look directly into the beam projected from the laser. Use caution when shining the laser on highly polished or reflective surfaces. Laser safety glasses help reduce laser beam glare. Always wear laser safety glasses when using the laser. Note that laser safety glasses are not designed to protect eyes from direct laser exposure.


1. (Using the Gen IV V8 engine as an example), observe and mark the serpentine belt orientation.

2. Remove the serpentine belt from the accessory drive system.

3. Install the tool onto the power steering pulley. Position the legs of the tool into the outer grooves of the pulley, farthest from the front of the engine.

4. Install the retaining cord around the pulley and to the legs of the tool.

5. Put on the laser safety glasses provided with the tool.

6. Depress the switch on the rear of the tool to activate the light beam.

7. Rotate the power steering pulley as required to project the light beam onto the crankshaft balancer pulley grooves.

8. Inspect for proper power steering pulley alignment.

   a. If the laser beam projects onto the second rib or raised area, the pulleys are aligned properly.

   b. If the laser beam projects more than one-quarter rib (0.035 in.) misalignment, adjust the position of the power steering pulley as required. (refer to the service manual for power steering pulley removal and installation procedures).

9. Install the serpentine belt to the accessory drive system in the original orientation.

10. Operate the engine and verify that the belt noise concern is no longer present.


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