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 Chev & GMC S/T & 'M' Vans with 2.5L L4 Gas Engine (RPO LN8)

#### TO: ALL AFFECTED DEALERS:

General Motors of Canada has determined that some 1986 Chev & GMC S/T Light Duty Trucks and Astro and Safari Van Models equipped with 2.5L L4 gas engine (RPO LN8) may have been produced with blocked cylinder head coolant passages. This condition can cause audible spark knock and/or engine overheating.

To determine if a 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.

#### VEHICLES INVOLVED:

Involved are certain 1986 S/T Chev & GMC Light Duty Trucks, and Astro and Safari Van Models equipped with 2.5L L4 gas engine and built within the following vehicle identification number (VIN) breakpoints:

#### Model Plant From Through ----- ----- ---- ------- CHEV ---- S/T-10 Moraine G2193946 G2208296 Shreveport G8180953 G8189777

Astro Van Baltimore GB204352 GB217668

GMC

S/T-15 Moraine G2521355 G2525139 Shreveport G8522855 G8524949

Safari Van Baltimore GB524784 GB528187

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 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

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 for this modification should be ordered through regular channels, as follows:

Part No. Description Per Vehicle

Bulk Stock Coolant 1/2 Qt. 10007449 Thermostat Hsg. Gasket 1

When cylinder head replacement is required, the following additional parts should be ordered. These parts should be ordered only when required.

Quantity Part No. Description Per Vehicle -------- ----------- ------------ 10037283 Cylinder Head 1 10035039 Cylinder Head Gasket 1 10026023 Intake Manifold Gasket 1 10004804 Exhaust Manitold Gasket 1 3835333 Valve Stem Seals 8 1052915 RTV 1 Tube

#### PARTS AND LABOUR CLAIM INFORMATION:

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

Repair Code Operation Time Allowance ------------ ---------- --------------- 2A Inspect Cylinder Head See chart for blockage

3A Replace Cylinder Head See chart

FAILED LAB REPAIR PERFORMED PART NO. HRS ---------------- -------- --- 2A

Inspect Cylinder Head 1986 "S/T" Truck W/0 A/C 10007449 0.9

Inspect Cylinder Head 1986 "S/T" Truck With A/C 10007449 1.3

Inspect Cylinder Head 1986 "M" Van W/0 A/C 10007449 1.1

Inspect Cylinder Head 1986 "M" Van With A/C 10007449 1.8

3A

Replace Cylinder Head 1986 "S/T" Truck W/0 A/C or Cruise 10037283 6.4

Replace Cylinder Head 1986 "S/T" Truck With Cruise Only 10037283 6.6

Replace Cylinder Head 1986 "S/T" Truck With A/C Only 10037283 7.3

Replace Cylinder Head 1986 "S/T" Truck With A/C and Cruise 10037283 7.5

Replace Cylinder Head 1986 "M" Van W/0 A/C or Cruise 10037283 6.8

Replace Cylinder Head 1986 "M" Van With Cruise Only 10037283 7.0

Replace Cylinder Head 1986 "M" Van With A/C Only 10037283 8.1

Replace Cylinder Head 1986 "M" Van With A/C and Cruise 10037283 8.3

#### SERVICE PROCEDURE:

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

- Metal coat hanger - Straightened and approximately 12 inches long.

- 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 same 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 THROUGH 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 harness.

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 (see illustration). The probe is to be inserted a minimum of 3.5 inches into the right (passenger) side coolant passage and 4.5 inches into the left (driver's) side coolant passage. 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, ST-369-86, Section 6A1 for removal and installation procedures, then proceed to step 23.

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

24. Apply sealant GM P/N 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 mixed 50% with water.

26. Install Campaign Identification Label according to instructions contained in this bulletin.

#### SPECIFICATIONS:

--------------- Belt tension (old belts): W/A/C W/0 A/C ------ ------- Generator 400 N (90 lbs) 300 N (67 lbs) Air Conditioning 400 N (90 lbs)

Thermostat Housing Bolts: 27 N.m (20 ft lbs) 27 N.m (20 ft lbs)

Generator Mounting torque:

Rear Bolt 27 N.m (20 ft lbs) 27 N.m (20 ft lbs) Lower Mounting Bolt 50 N.m (37 ft lbs) 50 N.m (37 ft lbs) Adjusting Arm Bolt 27 N.m (20 ft lbs) 27 N.m (20 ft lbs)

Compressor Mounting Bolts:

Front 43 N.m (32 ft lbs) Rear 30 N.m (22 ft lbs)

#### 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 THROUGH 15 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 (see illustration). The probe is to be inserted a minimum of 3.5 inches into the right (passenger) side coolant passige and 4.5 inches into the left (driver's) side coolant passage. 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 Service Manual, ST-372-86, Section 6Al 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 P/N 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 mixed 50% with water.

21. Install Campaign Identification Label according to instructions contained in this bulletin.

#### SPECIFICATIONS

Belt tension (old belts):

Generator 300 N (67 lbs) Air Conditioning 400 N (90 lbs)

Thermostat Housing Bolts: 27 N.m (20 ft lbs)

Generator Mounting torque:

Top Bracket Bolt 27 N.m (20 ft lbs) Bottom Bracket Bolt 50 N.m (37 ft lbs) Nut at back brace 42 N.m (30 ft lbs)

Compressor Mounting Bolts:

Front 43 N.m (32 ft lbs) Rear 30 N.m (22 ft lbs)

#### 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 some 1986 S/T Chevrolet and GMC Light Duty Trucks, Astro and Safari Vans 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 GM Dealer. Parts are available. Pleasee 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 (2) hours, and an additional six and a half (6 1/2) 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.

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.

Further assistance, if required, may be obtained from the General Motors Zone Office nearest you. Your vehicle Owner's Manual provides the location and phone number of each respective Zone Office.

We are sorry to cause you this inconvenience; however, we have taken the 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.