CAMPAIGN: INCORRECT SPLASH SHIELD INSTALLED

Models: 1991 'K' Trucks

General Motors of Canada has determined that a defect which relates to motor vehicle safety exists in certain 1991 K 1-2 Pickup Trucks built at Fort Wayne Assembly Plant. These vehicles may have an incorrect front wheelhouse splash shield that may contact the rubber portion of the front brake hose, which could result in a sudden failure of the front hydraulic brake system. If this failure occurred, the rear brake system still functions, but increased stopping distance would be required. Loss of front braking at a time when minimum stopping distance is required could result in a vehicle crash without prior warning.

To prevent this condition from occurring, dealers are to inspect all suspect 'K' Model vehicles for incorrect splash shields and replace them with the correct parts. Additionally, where there is an incorrect splash shield, the brake hose will be replaced.

VEHICLES INVOLVED:

Involved are certain 1991 'K' 1-2 Pickup Trucks built at the Fort Wayne Assembly Plant within the following VIN breakpoints:

Number of Vehicles Involved Model Plant From Through ----------------- -------- --------- ---- -------- 15 1991 GMC Fort Wayne SOP EOP

33 1991 Chevrolet Fort Wayne SOP EOP

All affected vehicles have been identified by the VIN listing provided to involved dealers with this bulletin. Any dealer not receiving a listing was not shipped any of the affected vehicles.

DEALER CAMPAIGN RESPONSIBILITY:

Dealers are to perform this campaign on all involved vehicles at no charge to owners, regardless of kilometres traveled, age of vehicle, or ownership, from this time forward.

Whenever a vehicle subject to this campaign is taken into your new or used vehicle inventory, or it is in your dealership for service, you are to ensure the campaign correction has been made before selling or releasing the vehicle.

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

CAMPAIGN PROCEDURE

Refer to Section 4 of the Service Policies and Procedures Manual for the detailed procedure on handling Product Campaigns. Dealers are requested to complete the campaign on all transfers as soon as possible.

OWNER NOTIFICATION:

All owners of record at the time of campaign release are shown on the attached computer listing and have been notified by first class mail from General Motors. The listings provided are for campaign activity only and should not be used for any other purpose.

PARTS INFORMATION:

Parts required to complete this campaign should be ordered through regular channels, as follows:

Part Number Description Quantity/Vehicle ----------- ------------- ---------------- 15569497 Splash Shield 1 Per Side (As Required)

17988191 Frt. Brake Hose-LH (K1) (K2 W/C5Z) As Required

17988192 Frt. Brake Hose-RH (K1) (K2 W/C5Z) As Required

PARTS AND LABOUR CLAIM INFORMATION:

Credit for the campaign work performed will be paid upon receipt of a properly completed campaign claim card or DCS transmission in accordance with the following:

Repair Code Description Time Allowance ----------- -------------------------- -------------- 1A Inspect for correct Splash Shields .3 If correct, no further action required

2A Replace One Brake Hose and One Shield .8

3A Replace Both Brake Hoses and Shields 1.0

Time allowance includes 0. 1 hour for dealer administrative detail associated with this campaign. Parts credit will be based on dealer net plus 30% to cover parts handling.

SERVICE PROCEDURE:

A. INSPECTION

1. Open hood of 'K' 1-2 vehicle to be inspected.

2. Observe both right and left splash shields of vehicle from the engine compartment and from the wheelhouse opening.

3. Compare the general shape of the splash shield to the illustration marked (Figure 1 - correct shield). Also note if the splash shield is resting against the brake lines.

4. If the general shape of the splash shield DOES NOT agree with Figure 1, then the splash shield will have to be replaced with the correct part number shield.

5. For reference only, Figure 2 shows the outline of the incorrect splash shield. This shield should be replaced with the correct shield.

6. For shield replacement continue to Section B, Replacement of Splash Shield and Brake Hose.

B. REPLACEMENT OF SPLASH SHIELD AND BRAKE HOSE

1. Remove existing splash shield's plastic retainer fasteners.

2. If the unit is equipped with the incorrect splash shield, then remove existing splash shield and brake hose. Install the correct splash shield with the existing fasteners and install a new brake hose. (For brake hose replacement: See below).

3. Install new splash shields by lining up hole patterns and pushing in existing retainers.

4. Install "Campaign Identification Label."

Hose Replacement

Clean dirt, grease, and other foreign material off the hose fittings at both ends.

Remove or Disconnect

1. Steel pipe 2. Clip or nut 3. Bolt 4. Washers 5. Hose

Install or Connect

o Use new copper washers when installing the hose.

1. The hose must not be twisted.

Important: The hose installation must not contact any suspension components.

1. Washers 2. Bolt 3. Clip or nut 4. Steel pipe

o Bleed the brakes. See below.

Manual Bleeding

o Delete the vacuum reserve by applying the brakes several times with the ignition switch in the "OFF" position.

NOTICE: Brake fluid will damage painted surfaces. Brake fluid can also damage electrical connections. Use shop cloths, suitable containers, and fender covers to prevent brake fluid from contacting such surfaces. Always reseal and wipe brake fluid containers clean to prevent spirage.

1. Fill the master cylinder reservoirs with New Improved Delco Supreme No. 1 1 Hydraulic Brake Fluid (GM P/N 992669) or an equivalent DOT 3 motor vehicle brake fluid.

o Remove the forward brake pipe connection at the master cylinder. o Allow brake fluid to flow from the connector port. o Connect but do not tighten the brake pipe.

2. Slowly apply die brake pedal allowing the air to bleed from the loose fitting.

o Tighten the fitting before releasing the pedal. o Wait 15 seconds and repeat this sequence, including the 15 second wait until all the air is purged from the bore.

3. After all the air has been removed from the forward connection, disconnect the rear pipe.

o Allow brake fluid to flow from the connector port. o Connect the brake pipe but do not tighten.

4. Slowly apply the brake pedal allowing the air to bleed from the loose fitting.

o Tighten the fitting before releasing the pedal. o Wait 15 seconds and repeat this sequence, including the 15 second wait until all the air is purged from the bore.

5. If it is known that the rest of the system does not contain any air, proceed to Step 11. Otherwise, finish bleeding in the following sequence.

6. Bleed die isolation/Dump Valve (RWAL applications). Refer to 1991 Sierra Service Manual X-9131 "REAR WHEEL ANTILOCK BRAKES" (Sec. 5A3).

7. Bleed each wheel in the following sequence:

o Right Rear o Left Rear o Right Front o Left Front

8. Attach a hose to the wheel cylinder/caliper bleeder screw.

o Immerse the opposite end of the hose into a container partially filled with clean brake fluid.

9. Slowly apply the brake pedal one time and hold.

o Loosen the bleeder screw to purge the air from the wheel cylinder/ caliper. o Tighten the bleeder screw and slowly release the pedal. o Wait 15 seconds, then repeat this sequence, including the 15 second wait until all the air is purged from the wheel cylinder/caliper.

10. Continue Steps 9 and 10 at each wheel until the entire brake system has been bled.

11. Check the brake pedal for "sponginess" and the brake warning lamp for an indication of an unbalanced pressure.

o Repeat the entire bleeding procedure to correct either of these two conditions.

Pressure

The pressure bleeding equipment must be of the diaphragm type. It must have a rubber diaphragm between the air supply and the brake fluid to prevent air, moisture, oil, and other contaminants from entering the hydraulic system. Use extreme care to prevent brake fluid from contacting any painted surface.

Tools Required:

J-29567 - Brake Bleeder Adapter (Plastic Reservoir) J-35856 - Combination Valve Depressor

NOTICE: It is very important that the correct master cylinder bleeder adapter is used to avoid possible damage to the master cylinder reservoir.

NOTICE: Brake fluid will damage painted surfaces. Brake fluid can also damage electrical connections. Use shop cloths, suitable containers, and fender covers to prevent brake fluid from contacting such surfaces. Always reseal and wipe brake fluid containers clean to prevent slippage.

1. Fill the pressure tank at least 1/3 full of brake fluid. The bleeder must be rebled each time fluid is added. o Charge the bleeder to 140 - 170 kPa (20 to 25 psi).

2. Use J-35856 to depress and hold the valve stem on the combination valve during the bleeding operation. o Install the bleeder adapter so the leg with the release valve is towards the cowl.

3. Connect the hose from the bleeder to the adapter at the master cylinder. o Open the tank valve.

4. Bleed the isolation/Dump Valve (RWAL applications). Refer to 1991 Sierra Service Manual X-9131 "REAR WHEEL ANTILOCK BRAKES" (Sec. 5A3).

5. Bleed each wheel in the following sequence: o Right Rear o Left Rear o Right Front o Left Front

6. Attach a hose to a brake bleeder screw. o Immerse the opposite end of the hose into a container partially filled with clean brake fluid.

7. Open the bleeder screw at least 3/4 of a tum and allow the fluid to flow until no air is seen in the fluid. o Close the bleeder screw.

8. Repeat from Step 6 at all the wheels.

9. Check the brake pedal for "sponginess," repeat the entire bleeding procedure if this condition is found.

10. Remove J-35856. o Disconnect the hose from the bleeder adapter. o Remove bleeder adapter.

11. Fill the master cylinder to the proper level with the brake fluid.

INSTALLATION OF CAMPAIGN IDENTIFICATION LABEL

Clean surface of radiator upper mounting panel and apply a Campaign Identification Label. Make sure the correct campaign number is inserted on the label. This will indicate that the campaign has been completed.

Dear General Motors Customer.

General Motors of Canada has determined that a defect which relates to motor vehicle safety exists in certain 1991 K 1-2 Pickup Trucks built at Fort Wayne Assembly Plant. These vehicles may have an incorrect front wheelhouse splash shield that may contact the rubber portion of the front brake hose, which could result in a sudden failure of the front hydraulic brake system. If this failure occurred, the rear brake system still functions, but increased stopping distance would be required. Loss of front braking at a time when minimum stopping distance is required could result in a vehicle crash without prior warning.

To prevent this condition from occurring, dealers will inspect all suspect 'K' Model vehicles for incorrect splash shields and replace them with the correct parts if required. Additionally, where there is an incorrect splash shield, the brake hose will be replaced. This service will be completed for you at no charge.

Please contact your GM dealer as soon as possible to arrange a service date.

This letter identifies your vehicle. Presentation of this letter to your dealer will assist their Service personnel in completing the necessary correction to your vehicle in the shortest possible time.

Subsequent to contacting your dealer, further assistance, if required, may be obtained from our Customer Assistance Centre, toll free, by calling 1-800-263-3777 (English), or 1-800-263-7854 (French).

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

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.