POP NOISE FROM WINDSHIELD PILLAR AREA (DIAG. INSTRUCT.)
SUBJECT: "POP" NOISE FROM WINDSHIELD PILLAR AREA MODELS: 1983-93 S/T TRUCKS
REFERENCE COWL "POP" TAPPING NOISE GMC TRUCK SERVICE BULLETIN NUMBER 91-2-122 (CORPORATE NUMBER 162001R), GROUP 2-FRAME-BUMPER-SHEET METAL , DATED JULY 1991.
Owners of some 1983-93 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 Truck Service Bulletin GMC Number 92-10-130, Group 10-Body Section, Corporate Number 261610, dated September 1992.
2. Loose door lock rods may vibrate during vehicle operation creating a rattle type noise.
Refer to "Front Door Lock Rod Rattle" Truck Service Bulletin GMC Number 91-10-144, Group 10-Body Section, Corporate Number 161603, dated September 1991.
Also refer to "Unwanted Sound: Squeaks and Rattles Diagnosis and Correction" Reference Manual.
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.
Refer to the "Unwanted Sound: Squeaks and Rattles Diagnosis and Correction" Reference Manual.
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.
Refer to the "Unwanted Sound: Squeaks and Rattles Diagnosis and Correction" Reference Manual.
8. An air vent "itch" may occur if the louvered vent and A/C duct rub together.
Refer to the "Unwanted Sound: Squeaks and Rattles Diagnosis and Correction" Reference Manual.
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 GMC Truck Service Builetin Number 91-10-20, Group 10-Body Section, Corporate Number 061006, dated September 1990.
Also refer to "Unwanted Sound: Squeaks and Rattles Diagnosis and Correction" Reference Manual.
Illustrations and instructions are available in the Revised "Unwanted Sound: Squeaks and Rattles Diagnosis and Correction" Reference Manual Number GMC TT-91-03-2. The Reference Manual was provided to dealers in 1991. Order forms for additional Reference Manuals (with video) can be pro cured by calling (313) 456-4679.
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.
