CAMPAIGN:CYLINDER HEAD BLOCKED INSPECT AND REPLACE HEAD. GMC Truck S15 Pickup - 4WD 1986

For 1990-2009 cars

# CAMPAIGN:CYLINDER HEAD BLOCKED INSPECT AND REPLACE HEAD

#### MODELS: 1986 S/T TRUCK AND M15 SAFARI VAN WITH 2.5L L4 GAS ENGINE (RPO LN8)

General Motors has determined that some 1986 GMC S/T15 Light Duty Truck and M15 Safari Van Models equipped with 2.5L L4 gas engines (RPO LN8) may have been produced with blocked cylinder head coolant passages. This condition can cause audible spark knock and/or engine overheating. To prevent the possibility of this condition occurring it will be necessary to inspect all involved vehicles for coolant passage blockage, and if a blockage is found, replace the cylinder head.

#### VEHICLES INVOLVED

Involved are certain 1986 GMC S/T15 trucks and M15 Safari Vans equipped with 2.5L L4 gas engines built within the following VIN breakpoints:

#### Model Year Model Plant From To ---- ----- ----- ---- -- 1986 S/Tl5 Moraine G2521355 G2525139 1986 S/Tl5 Shreveport G8522855 G8524949 1986 MVan Baltimore GB524784 GB528187

The specific vehicles involved in this campaign have been identified by Vehicle Identification Number Computer Listings. These listings are furnished to all involved dealers with the campaign bulletin.

DEALER CAMPAIGN RESPONSIBILITY

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. Whenever a vehicle subject to this campaign is taken into your new or used vehicle inventory, or it is in your dealership for service in the future, you should take the steps necessary to be sure the campaign correction has been made before reselling 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 mod- ification according to instructions contained in this bulletin. If no owner's name and address were available to GMC Truck at the time of campaign initiation, the dealer will 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 General Motors Corporation 101 Union Street Plymouth, Michigan 48170

#### OWNER NOTIFICATION

Owners will be notified of this campaign on their vehicles by GMC Truck (see copy of Owner Letter included with this bulletin). A listing of owner names and addresses has been 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

It is necessary to make a probe out of one of the following:

o Metal coat hanger-straightened and cut approximately 12 inches long

o Dipstick-cut off twisted end

Place a permanent mark 3.5 inches and 4.5 inches from one end of the probe. Then one inch from this end, put a 45 degree bend in the probe. (See illustration)

S/T Truck (with or without air conditioning) ------------------------------------------- 1. Disconnect battery cable.

2. Drain engine of all coolant. Use a clean container and save the coolant for re-use.

3. Loosen generator adjustment bolts.

4. Remove generator belt.

5. Remove generator adjustment bolts.

6. Disconnect throttle cable at the intake manifold.

7. Remove generator adjustment pivot bracket and lay generator aside.

8. Disconnect coolant sensor wire.

9. Disconnect hose at thermostat housing.

10. Disconnect strut rod bracket at generator front bracket.

11. Remove generator front bracket.

12. Disconnect electrical harness at thermostat.

Items 13 thru 18 apply to trucks equipped with air conditioning.

13. Disconnect electrical harness at air conditioning compressor.

14. Remove air conditioning compressor belt.

15. Remove air conditioning compressor bracket.

16. Disconnect air conditioning compressor hamess.

17. Remove air conditioning compressor from bracketry and lay aside.

18. Remove air conditioning compressor front support bracket.

19. Disconnect upper radiator hose at thermostat housing.

20. Remove vacuum line bracket from thermostat housing.

21. Remove thermostat housing.

22. Insert the probe into the two cooling passages, Figure 1. The probe is to be inserted a minimum of 3.5 inches into the right coolant passage (pas- senger side of vehicle) and 4.5 inches into the left coolant passage (driver's side of vehicle). If this can be done no further action is required. Proceed to step 23. If the probe will not slide into one or both passages even after several attempts, the cylinder head must be replaced. Refer to S/T Truck Service Manual X-8629 (Section 6A1-8) for removal and installation procedures, then proceed to step 23.

23. Clean the thermostat housing and cylinder head of all old sealant.

24. Apply sealant GM part number 1052915 or equivalent to the thermostat housing and install to the cylinder head.

25. Reverse steps 1-21 for parts reinstallation. Refill cooling system using original coolant. Top off coolant with GM part number 1052753 or equiv- alent mixed 50 percent with water.

#### SPECIFICATIONS

Belt tension (old belts):

With Without AC AC -- -- Generator 400 N (90 lb) 300 N (67 lb) Air conditioning 400 N (90 lb)

Thermostat Housing Bolts: 27 N-m (20 lb ft) 27 N-m (20 lb ft)

Generator Mounting Torque: Rear Bolt 27 N-m (20 lb ft) 27 N-m (20 lb ft) Lower Mounting Bolt 50 N-m (37 lb ft) 50 N-m (37 lb ft) Adjusting Arm Bolt 27 N-m (20 lb ft) 27 N-m (20 lb ft)

Compressor Mounting Bolts: Front 43 N-m (32 lb ft) Rear 30 N-m (22 lb ft)

#### M Van (with or without air conditioning)

1. Disconnect battery cable.

2. Drain engine of all coolant. Use a clean container and save the coolant for re-use.

3. Remove air intake and extension duct.

4. Remove oil fill tube.

5. Remove vacuum line bracket.

6. Remove upper radiator hose.

7. Remove generator belt.

8. Disconnect throttle cable at the intake manifold.

9. Remove generator adjustment pivot bracket.

10. Remove generator front bracket.

11. Disconnect hose at thermostat housing.

12. Disconnect electrical harness at thermostat.

Items 13 thru 18 apply to trucks equipped with air conditioning.

13. Disconnect electrical harness at air conditioning compressor.

14. Remove air conditioning compressor belt.

15. Remove air conditioning compressor bracket.

16. Remove thermostat housing.

17. Insert the probe into the two cooling passages, Figure 1. The probe is to be inserted a minimum of 3.5 inches into the right coolant passage (passenger side of vehicle) and 4.5 inches into the left coolant passage (driver's side of vehicle). If this can be done, no further action is required. Proceed to step 18. If the probe will not slide into one or both passages even after several attempts, the cylinder head must be replaced. Refer to the Safari Service Manual X-8630 (Sec- tion 6A1-9) for removal and installation instructions, then proceed to step 18.

18. Clean the thermostat housing and cylinder head of all old sealant.

19. Apply sealant GM part number 1052915 or equivalent to the thermostat housing and install to the cylinder head.

20. Reverse steps 1-16 for parts reinstallation. Refill cooling system using original coolant. Top off coolant with GM part number 1052753 or equivalent mixed 50 percent with water.

#### SPECIFICATIONS:

-------------- Belt tension (old belts): Generator 300 N (67 lb) Air Conditioning 400 N (90 lb)

Thermostat Housing Bolts: 27 N-m (20 lb ft)

Generator Mounting Torque: Top Bracket Bolt 27 N-m (20 lb ft) Bottom Bracket Bolt 50 N-m (37 lb ft) Nut at Back Brace 42 N-m (30 lb ft)

Compressor Mounting Bolts: Front 43 N-m (32 lb ft) Rear 30 N-m (22 lb ft)

#### PARTS INFORMATION

A. Parts Needed for Inspection

Quantity Description Part Number -------- ----------- ----------- 1/2 Qt. Coolant(1.07 Qt.) 1052754 (55 Gal.) 1 Thermostat Housing Gasket 10007449

B. Parts Needed for Replacement

Quantity Description Part Number -------- ----------- ----------- 1/2 Qt. Coolant (1.07 Qt.) 1052754 (55 Gal.) 1/4 Tube RTV 1052915 1 Cylinder Head 10037283 1 Cylinder Head Gasket 10035039 1 Inlet Manifold Gasket 10026023 1 Exhaust Manifold Gasket 10004804 1 Thermostat Housing Gasket 10007449 8 Seals-Valve Stem 3835333

Parts are to be obtained from the Warehousing and Distribution Division of General Motors (WDDGM).To ensure that these parts will be obtained as soon as possible, they should be ordered from WDDGM on a C.I.O. order with no special instruction code, but order on an advise code (2).

#### WARRANTY INFORMATION

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

Labor Operation *Time Trouble Number Description Allowance Code

Inspect cylinder head as outlined in the service procedure-No further action required V3670 S/T Truck Without AC .8 hr. 96 Wth AC 1.2 hr. V3676 M Van Without AC 1.0 hr. 96 With AC 1.7 hr. Inspect cylinder head as outlined in the service procedure and replace cylinder head V3672 S/T Truck WithoutAC 6.3 hr. 96 WithAC 7.2 hr. WithAC& 7.4 hr. Cruise Without AC 6.5 hr. & with Cruise V3678 M Van Without AC 6.7 hr. 96 With AC 8.0 hr. With AC 8.2 hr. & Cruise Without AC 6.9 hr. & with Cruise

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

Dear GMC Truck Owner:

General Motors has determined that some 1986 S/T-15 light duty truck and M15 Safari van models equipped with 2.5L L4 gas engine may have been produced with blocked cylinder head coolant passages.

This condition can cause audible spark knock and/or engine overheating.

To determine if your vehicle may be affected by this condition, it will be necessary to inspect the coolant passage for blockage. If blockage is found, the cylinder head will be replaced.

Instructions have been sent to your GMC Truck dealer. Parts are available. Please contact your dealer to arrange a service date. The inspection, and if necessary cylinder head replacement, will be performed at no charge to you. The inspection will take approximately two hours, and an additional six and a half hours may also be needed if cylinder head replacement is required. Please ask your dealer if you wish to know how much additional time is needed to process your vehicle.

The enclosed owner reply card identifies your vehicle. Presentation of this card to your dealer will assist in making the necessary correction in the shortest possible time. If you have sold or traded your vehicle, please let us know by completing the postage paid owner reply card and returning it 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 GENERAL MOTORS CORPORATION

#### CAMPAIGN IDENTIFICATION LABEL

Each vehicle modified 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 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 "GMC Truck Claims Processing Manual" #SD8519.

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.