CAMPAIGN: COOLANT LEAK FROM AUXILIARY REAR HOSE ASSY.. GMC Truck GMC C Pickup

SUBJECT: COOLANT LEAK FROM THE AUXILIARY REAR HEATER HOSE ASSEMBLY

MODELS: 1992 C/K SUBURBANS EQUIPPED WITH 7.4L ENGINES (Ll9) AND AUXILIARY REAR HEATER (C36)

REFERENCE: DCS MESSAGE DATED JUNE 12, 1992 "STOP DELIVERY ON 1992 SUBURBAN MODELS WITH L19 AND C36". VEHICLES MAY BE DELIVERED AFTER COMPLETING THE FOLLOWING PROCEDURE.

General Motors has determined that certain 1992 C/K Suburbans equipped with 7.4L engines (Ll9) may develop an engine coolant leak from the auxiliary rear heater outlet hose (C36). The leak is caused by a heat deterioration of the hose material as a result of its close proximity to the right-hand exhaust manifold. The leak could eventually result in a total loss of engine coolant.

To correct this condition a new rear heater inlet/outlet hose assembly with protective heat insulation will be installed.

VEHICLES INVOLVED

Involved are certain 1992 C/K Suburbans with 7.4L engines (Ll9) and auxiliary rear heater (C36) built within the following VIN breakpoints:

MODEL MAKE MODEL YEAR PLANT FROM THROUGH ---- ----- ----- ----- ---- ------- GMC C/K 20906 1992 Janesville SOP NJ722495

The specific vehicles involved in this campaign will be identified by Vehicle Identification Number Computer Listings. These listings will be furnished to all involved dealers.

DEALER CAMPAIGN RESPONSIBILITY

All unsold new vehicles in dealers' possession and subject to this campaign MUST be held and inspected/repaired per the service procedure of this campaign bulletin BEFORE owners take possession of these vehicles.

Dealers are to service all vehicles subject to this campaign at no charge to owners, regardless of mileage, age of vehicle, or ownership, from this time forward.

Owners of vehicles recently sold from your new vehicle inventory are to be contacted by the dealer and arrangements made to make the required correction according to instructions contained in this bulletin.

In summary, whenever a vehicle subject to this campaign enters your vehicle inventory, or is in your dealership for service in the future, please take the steps necessary to be sure the campaign correction has been made before selling or releasing the vehicle.

If the name and address of the owner of an involved vehicle was unavailable to GMC Truck Division at the time of campaign initiation, the dealer must determine the owner's name and address from the dealership sales records. Please provide this information directly on the second copy of the listing next to the applicable VIN so that our records may be updated and the appropriate notification mailed to the owner. This second copy should then be submitted to the address listed below in the previously supplied yellow campaign envelopes.

GMC Truck Division General Motors Corporation 101 Union Street Plymouth, Michigan 48170

OWNER NOTIFICATION

Owners will be notified of this campaign on their vehicles by GMC Truck Division (see copy of owner letter included with this DCS Message). A listing of owner names and addresses will be furnished to the involved dealers to enable dealers to follow up with owners involved in this campaign. This listing may contain owner names and addresses obtained from State Motor Vehicle Registration records. The use of such motor vehicle registration data for any other purpose is a violation of law in several states. Accordingly, you are urged to limit the use of this listing to this campaign.

SERVICE PROCEDURE

1. Replace the auxiliary heater inlet and return hose assembly with the new design auxiliary heater inlet and hose assembly following the procedure found in the 1992 C/K Truck Service Manual X-9231 Page 1A-21.

NOTE: With a clean drain pan, retain and reuse coolant drained from the system.

2. Loosen the two fasteners which secure the air intake pre-cleaner bracket to the wheel well. They are located inside the passenger side front wheel well.

3. Loosen the single fastener which secures the auxiliary heater pipe assembly to the air intake pre-cleaner bracket.

4. By pulling/pushing/rotating the auxiliary heater pipe assembly, use the relative movement between the loosened components to maximize the distance between the auxiliary rear heater hose assembly and the exhaust manifold.

5. Once the maximum distance is obtained, hold the position and retorque the air intake pre-cleaner bracket fasteners to 18 Nm (159 in.lbs.) and the auxiliary heater pipe assembly fastener to 18 Nm (159 in.lbs.).

6. Using a shop scale, measure the distance between the auxiliary rear heater hose assembly and the passenger side exhaust manifold at their closest point. One half inch (112") clearance is a required minimum. If the required minimum is not obtained repeat steps 2 through 6. If minimum clearance is still not obtained the air inlet pre-cleaner bracket and auxiliary heater pipe assembly bracket can be removed and the holes in the wheel well and auxiliary heater pipe assembly bracket can be elongated or enlarged to allow more clearance.

7. Install a "Campaign Identification Label"

CAMPAIGN IDENTIFICATION LABEL

Each vehicle corrected in accordance with the instructions outlined in this Product Campaign Bulletin will require a "Campaign Identification Label." Each label provides a space to include the campaign number and five (5) digit dealer code of the dealer performing the campaign service. This information may be inserted with a typewriter or ball point pen.

Each "Campaign Identification Label" is to be located on the radiator core support in an area which will be visible when the vehicle is brought in for periodic servicing by the owner.

Apply "Campaign Identification Label" only on a clean, dry surface.

ADMINISTRATIVE PROCEDURE

Procedures covering this campaign are outlined in Section V of your dealership's "GM Truck Claims Processing Manual" #P9119.

PARTS INFORMATION

Parts required to complete this campaign will be pre-shipped to involved dealers by General Motors Service Parts Operation (GMSPO). If additional parts are required, they may be obtained from General Motors Service Parts Operation (GMSPO). To ensure that these parts will be obtained as soon as possible, they should be ordered from GMSPO on a C.I.O. order with no special instruction code but order under an advise code (2).

Part Number Description Quantity ------ ----------- -------- 15961911 C-Truck: Auxiliary Heater Hose Assembly 1 or 15961912 K-Truck: Auxiliary Heater Hose Assembly 1

WARRANTY INFORMATION

Dealers should submit a warranty claim on each vehicle completed under this campaign.

LABOR OPERATION *TIME TROUBLE NUMBER DESCRIPTION ALLOWANCE CODE --------- ----------- --------- ------- V7630 Replace Auxiliary 0.7 Hrs. 96 Heater Inlet and Return Hose Assembly

ADD: Enlarge holes in wheel 0.2 Hrs. well and auxiliary heater pipe assembly bracket.

* For dealer to receive Administrative Time Allowance associated with this campaign, add 0.1 hour to the Labor Operation Time Allowance.

COPY OF OWNER LETTER

Dear GMC Truck Owner:

Our records show that you own one of our new 1992 GMC C/K Suburbans. The rate at which these trucks have been accepted into the stream of commerce has been very gratifying to us. In addition, feedback from customers, dealers and our own tracking systems indicate a very high degree of product reliability thus far.

We have recently become aware of a situation on certain 1992 Suburbans equipped with 7.4L engines. These vehicles may develop an engine coolant leak from the auxiliary rear heater outlet hose. The leak is caused by a heat deterioration of the hose material as a result of its close proximity to the right-hand exhaust manifold. If left unattended, the leak could eventually result in a total loss of engine coolant.

To correct this condition a new rear heater inlet/outlet hose assembly with protective heat insulation will be installed. This service will be completed for you at no charge.

Please contact your GMC Truck dealer as soon as possible to arrange a service date. Instructions for making this correction have been sent to your dealer. Please ask your dealer if you wish to know how much time will be needed to schedule, process and repair your vehicle.

The enclosed postage paid owner reply card identifies your vehicle. Presentation of this card to your dealer will assist in making the necessary correction to your vehicle in the shortest possible time. If you have sold or traded your vehicle, please furnish us complete name and address of the person you sold or traded your vehicle to and return the card to us.

We are sorry to cause you this inconvenience; however, we have taken this action in the interest of your continued satisfaction with our products.

GMC TRUCK DIVISION GENERAL MOTORS CORPORATION

92Cl9 Enclosure

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.