Technical Service Bulletins

Fixing Infiniti drive belt noise

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Fixing Infiniti drive belt noise

If an Infiniti engine exhibits an apparent drive belt noise, follow the flow chart (seen here) to determine the cause.


Example: Max angular pulley movement (mm)

FX45, M45                         VK45 (Alt)         7

FX45, M45                         VK45 (P/S)       13

FX50                                   VK50 (Alt)         7

FX50                                   VK50 (P/S)      13

QX56                                  VK56                7

EX35, FX35, G35, M35    VQ35HR          16

G37 COUPE, G37            VQ37                16

1. With the engine running at idle and the AC turned on, observe pulley angular movement (side-to-side). Visual comparison of movement with a known good vehicle is recommended. Refer to Figure 1.

2. With the engine running at idle and the AC turned on, observe the pulley axial/lateral movement (back and forth). Maximum movement specification is 1mm. Refer to Figure 2.


No more than 1mm of pulley rock should be visible. Refer to Figure 3.


NOTE: The following steps can be performed while the alternator is installed on the engine if the drive belt is removed and the alternator electrical connections are disconnected.

1. Secure the rotor using a medium size screwdriver and a rolled shop towel.

2. Turn the pulley clockwise when viewed from the front. The pulley should be locked. If it rotates in both directions, replace the alternator.

3. Turn the pulley counterclockwise when viewed from the front. The pulley should turn with some dragging. If it locks or has unusual resistance, replace the alternator.

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