Cold Start Belt Chirp - keywords AC A/C accessory air bracket compressor conditioning diesel drive engine idle LBZ LLY mounting noise PIP3138B PIP3965 PIP3965A power pump rattle squeal squeak steering

This PI was revised to include a new accessory drive belt part number. Please Discard PIP3965

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

The customer concern may be a accessory drive belt chirp, squeal, or squeak noise at idle. The noise may be reduced or gone after the engine warms up.

2004-2007 C/K trucks with a 6.6L LLY engine produced before June, 2004 may have an A/C compressor/power steering pump mounting bracket and power steering rear mounting bracket that are machined slightly out of specification.

Vehicles built with a 6.6L LLY or LBZ engine after June 2004 will already have the new A/C compressor/power steering pump mounting bracket installed, but still may exhibit belt noise caused by the power steering pump rear mounting bracket and/or Power Steering Pulley alignment.

Please refer to bulletin number 05-06-01-018 for 2004 to 2005 vehicles and belt chirp.

For the 2006 and 2007 LBZ and LLY engines complete the procedure below.

1. Remove the rear power steering bracket bolts that bolt to the A/C compressor/power steering pump bracket.



2. Loosen the front power steering pump bracket bolts that bolt to the A/C compressor/power steering pump bracket.



3. When reinstalling the bracket, torque the front mounting bolts to 50Nm (37 lb ft). Do not reinstall the rear power steering mounting bolts that bolt to the aluminum bracket. (The front power steering pump bracket bolts must always be tightened first to ensure correct pulley/bracket alignment)
4. Use a mirror and flashlight to observe the alignment between the rear power steering bracket bolt holes and bolt holes in the aluminum bracket. If the holes are aligned properly install the bolts and torque to 50Nm (37 lb ft).
5. If the holes do not align properly replace the rear power steering bracket with part number 97209551.
6. Install the rear bracket and torque bolts to 50Nm (37 lb ft).

Note: If the noise was not fully eliminated, the Power Steering Pulley may be adjusted inward or outward (from the flush position) on the pump shaft a maximum of 1 mm (.039") to assist in eliminating any remaining belt noise. Pulley adjustments should be made in small increments.

The alignment instructions must be followed because the power steering pulley alignment is critical for the repair of the cold start belt chirp. If there is a belt chirp noise after the belt/pulley alignment has been checked, there is a new drive belt that may help with the cold start belt chirp. Belt part numbers are listed below:

2006-2007 C/K Trucks with LLY and LBZ engine: 98035628

2006-2007 G Van with LLY engine: 98035630

New belts are not available for dual generator systems. If a belt chirp noise is occurring on a dual generator system please complete a Field Product Report (FPR).

Instructions for a completing a FPR can be found in bulletin number 02-00-89-002F..

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.