POP NOISE FROM WINDSHIELD PILLAR AREA (DIAG. INSTRUCT.)

SUBJECT: POP NOISE FROM WINDSHIELD PILLAR AREA

MODEL and YEAR: 1983-93 S/T TRUCKS

REFERENCE COWL "POP" TAPPING NOISE CHEVROLET DEALER SERVICE BULLETIN NUMBER 91-351 -1 0, DATED JUNE 1991.

Owners of some 1983-1993 S/T Pickups and Utilities may comment on a cowl "pop" noise transmitted through the "A" pillar. It has been determined that sections other than the windshield cowl area may produce a sound which imitates cowl "pop".

PRIOR TO PERFORMING ANY CORRECTION FOR COWL "POP" TAPPING NOISES, VERIFY THE SOURCE OF THE NOISE(S) TO DETERMINE IF IT IS A VALID COWL "POP" CONDITION.

Possible noise areas to check are:

- Instrument panel "itch"/noise.

- Loose door lock rods.

- Loose wires/harnesses contacting the wall of the engine/passenger compartment (cowl).

- A lack of door hinge lubrication.

- An Electronic Control Module (ECM) bracket "itch".

- An ash tray rattle.

- An air vent squeak.

- Hood hinge "flutter"/rattle.

INFORMATION:

----------- 1. INSTRUMENT PANEL (I/P) "ITCH"/NOISE sound at the front edge of the I/P may occur if the I/P pad rubs against the cowl/dash support panel.

Refer to "Instrument Panel Pad to Cowl Panel "Itch" Noise" Chevrolet Dealer Service Bulletin Number 92-286-10, dated Sept. 1992.

2. LOOSE DOOR LOCK RODS may vibrate during vehicle operation creating a rattle type noise.

Refer to "Front Door Lock Rod Rattle" Chevrolet Dealer Service Bulletin No. 91-406-10, dated August 1991.

3. THE ELECTRONIC CONTROL MODULE (ECM) WIRING HARNESS CLIP may not be properly attached at the transmission bellhousing bolt allowing contact with the floor pan/front of dash area. This sound may be amplified by the HVAC ductwork.

4. LOOSE WIRES/HARNESSES may be tapping against the engine/passenger compartment wall (cowl).

5. LACK OF DOOR HINGE LUBRICATION - Insufficient lubrication may create a binding/squeaking condition.

6. AN ECM BRACKET "ITCH" sound may occur if the ECM moves within its mounting bracket.

7. AN ASH TRAY BRACKET RATTLE coming from the ash tray or radio area of the instrument panel may occur if the bracket is loose and vibrating against the I/P.

8. AN AIR VENT "ITCH" may occur if the louvered vent and A/C duct rub together.

9. HOOD "FLUTTER"/RATTLE may occur if there is movement in the hood hinge attachment to the truck frame. Sound may accompany the hood movement.

Refer to Dealer Service Bulletin Number 91-181-10, Dated February 1991..

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.