CHASSIS SYSTEM UNDERBODY NOISE (DIAGNOSIS AND SUMMARY)

Subject: CHASSIS SYSTEMS RELATED UNDERBODY NOISE DIAGNOSIS AND SUMMARY

Model and Year: 1991-92LUMINA

THIS BULLETIN REVISES DEALER SERVICE BULLETIN NO. 90-113-10, DATED DECEMBER 1989. THE 1991-92 MODEL YEAR HAS BEEN ADDED AND ALL CHASSIS SYSTEMS AND ADDITIONAL NOISE CONDITIONS INCLUDED.

Some 1990-92 W-cars may exhibit various noises emanating from the underbody of the vehicle that may be caused by a variety of conditions related to the various chassis systems.

It is the intent of this bulletin to summarize prior issued bulletins and to provide insight into other conditions that have been noted.

When prior published bulletins are referenced, they should be utilized to insure proper service procedures are followed.

(A) SQUEAK/SQUAWK/ITCHING NOISE

Condition: I Squeaking/Itching from front of vehicle during a turning maneuver on 1990 vehicles assembled prior to breakpoints below:

Suspension VIN Level Breakpoint ---------- ---------- All Levels L9153753 (Oshawa 1)

L1137308 (Oshawa 2)

Cause:

Movement between strut mount cushion plastic stiffener, strut rod and/or strut mount cushion. Correction: Remove the plastic stiffeners from both of the front strut mount cushions (Reference Dealer Service Bulletin No. 90-113-3D). Condition: II Squawk from front of vehicle at low ambient temperatures and normal operation on 1990 vehicles assembled prior to breakpoints below:

VIN Breakpoint ---------- L9279163 (Oshawa 1)

L1201451 (Oshawa 2)

Cause:

Stabilizer shaft rotating in the power control arm stabilizer shaft insulators. Correction: Install new high compression lower control arm stabilizer shaft insulators, P/N 10152155 (Reference Dealer Service Bulletin No. 90-301-3C). Condition: III Squeaking during normal suspension/vehicle operation (1990 vehicles).

Cause:

Park brake cable movement through grommet in cable support brackets. Correction: Apply lubricant to cables in area of grommets (Reference Dealer Service Bulletin No. 90-125-5). Condition: IV Thumping/squawk noise from rear of vehicle, and most apparent when operated at low speeds over irregular road surfaces. Cause: A load spike caused by the strut jounce bumper system transmitting noise through the body strut tower structure. Correction: Replace both rear strut jounce bumper assemblies with new assemblies contained in service unit, P/N 22063945 (Reference Dealer Service Bulletin No. 92-82B-3D).

(B) THUD/CLUNK NOISE

Condition: I Thud/Clunk noise from rear of vehicle most apparent after a harsh/sharp road input such as a chuck-hole/speed bump (I 990-91 vehicles with auxiliary springs).

Cause:

Auxiliary rear spring lower attaching bracket not in full contact with rear spindle rod.

Correction:

Insure auxiliary rear springs lower brackets are properly seated on spindle rods (Reference Dealer Service Bulletin No. 91 -392-3D).

Condition: II Clunk noted during normal suspension/vehicle movements (1990 vehicles)

Cause: Exhaust system contacting rear stabilizer shaft.

Correction:

Inspect exhaust system and stabilizer shaft for witness marks due to metal-to-metal contact. Align exhaust system to provide adequate clearance if interference condition is noted.

Condition: III Thud/clunk from rear of vehicle after a harsh/sharp road input such as a chuck- hole/speed bump.

Cause:

Spindle rod bushing(s) loose in the spindle rod. Spindle rod cross section appears somewhat collapsed at open ends.

Correction:

Replace spindle rods.

Base Suspension Up Level Suspension --------------- ------------------- P/N 10062855 (Front) P/N 10062857 (Front) P/N 10152146 (Rear) P/N 10152147 (Rear)

Parts are currently available from GMSPO.

(C) RATTLE NOISE

Condition: I Metallic rattling during normal vehicle operation or engine run-up in neutral (1990 vehicles).

Cause:

Loose clinch nuts in either exhaust intermediate pipe or underbody hanger brackets. Correction: Install washer P/N 1 1 500367 between hanger and either or both the underbody and pipe brackets.

Condition: II Metallic rattling noted during engine run-up in neutral or normal suspension/vehicle operation. (1 990 vehicles).

Cause: Loose exhaust system heat shields.

Correction:

Inspect and tighten loose exhaust system heat shield fasteners insuring sufficient clearance is maintained.

Condition: III Dull rattling noted during normal suspension/vehicle operation (1990 vehicles)

Cause:

Park brake cable grommets not properly installed in underbody retaining brackets. Correction: Insure both underbody brackets are not distorted and install cable grommets (Reference Dealer Service Bulletin No. 90-125-5).

(D) OIL CANNING/POPPING NOISE

Condition: I Thumping/squawk noise from rear of vehicle, and most apparent when operated at low speeds over irregular road surfaces.

Cause:

A load spike caused by the strut jounce bumper system transmitting noise through the body strut tower structure.

Correction:

Replace both rear strut jounce bumper assemblies with new assemblies contained in service unit, P/N 22063945 (Reference Dealer Service Bulletin No. 92-82B-3D).

(E) CREAK/GROAN NOISE

Condition: I Creak/groan or, in severe instances, a clunk/thud noise during a vehicle twisting motion maneuver such as turning up a steep incline/driveway (I 989-91 vehicles).

VIN Breakpoint ---------- M9170499 (Oshawa 1)

M1 124665 (Oshawa 2)

Correction:

1990-91 vehicles prior to above VIN breakpoints.

Install new fuel tank straps, P/N 101 99250 and strap spacers, P/N 101 92675 (Reference Dealer Service Bulletin No. 91-232A-10).

1991 after VIN breakpoints.

Install new fuel tank straps, P/N 101 99250 (Reference Bulletin No. 91-232A-10).

(F) MOAN/BOOM NOISE

Condition: I Exhaust Moan/Boom 2300-2500 RPM range on 1991 vehicles with 3.4L engines (RPO LQ1) assembled prior to VIN breakpoints below:

VIN Breakpoint ---------- M9192950

Cause:

Exhaust system excited by engine exhaust pulse induced vibration.

Correction:

Install exhaust damper, P/N 10199232 (Reference Dealer Service Bulletin No. 91-275- 6F).

Part Availability:

Parts are currently available from GMSPO.

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.