INCREASED ENGINE NOISE (NEW A.I.R. ADAPTER)

SUBJECT INCREASED ENGINE NOISE / NEW A.I.R. ADAPTER MODELS: 1988-89 C3, K3 AND R2 TRUCKS W/7.4L (VIN CODE N)

CONDITION: Some 1988-89 C/K3, and R2 trucks with 7.4L engines and serpentine drive may receive customer comments of increased engine noise.

Cause: Tube assembly between the Air injection Reaction (A.I.R.) Mana tion Reaction (A.I.R.) Management Valve and A.I.R. pump may be cracked or broken.

Correction: A new design consisting of a bracket assembly, molded hose and adapter has been released. See the following Service Procedure:

SERVICE PROCEDURE:

(SEE ILLUSTRATION)

1. Remove old adapter

2. On trucks that DO NOT have the support tab on the adapter tube, temp- orarily install new design hose, bracket and hose adapter to determine hole location for bracket.

3. Trucks that DO HAVE the support tab on the adapte r tube will have one hole and weld nut already located on A/C Compressor / A.I.R. Pump Bracket.

4. On trucks with air conditioning, remove compressor from mounting bracket and lay to side. DO NOT DISCHARGE REFRIGERANT FROM SYSTEM.

5. On trucks without air conditioning, remove idler pulley bracket and save for reinstallation.

6. Scribe location of new bracket assembly on A/C compressor/A.I.R pump bracket.

7. Drill 5/16" hole/s in A/C bracket using new bracket assembly as template.

8. Install New Parts:

Part Description Quantity Number

10045710 Adapter One Required Asm. 10129577 Bracket One Required Asm. 10129578 Hose One Required 11508106 Bolt One or Two Required See Step 2 and 3 11507036 Nut One or Two Required See Step 2 and 3B Parts are currently available through GMSPO.

9. Torque all bolts to 20-27 N.m. (14-20 lbs. ft.).

10. Reinstall A/C Compressor or idler Pulley.

WARRANTY INFORMATION

Labor Operation Labor Time Models

Tl 620 C/K/R With Air .6 Hour Conditioning Tl 620 C/K/R Without .5 Hour Air Conditioning

NOTE: Labor Operation is coded to emissions coverage in the warranty system.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.