ENGINE OVERHEAT WHILE TOWING OR HEAVY USAGE

Model and Year 1988 C/K 2500-3500 SERIES WITH 7.4L AND 6.2L (VIN CODE N, C, J) ENGINE

Some 1988 C/K trucks equipped with 7.4L or 6.2L engines may experience an engine overheat (250 F - 260 F) while towing a trailer or under heavy usage, yet during normal operation, without a heavy load or trailer, the engine operates at a normal temperture (210 F - 235 F).

If the condition cannot be repaired using procedures in the Service Manual, the radiator core support opening should be inspected for the proper opening width. The truck should also be inspected for the presence of the lower radiator support baffle (see Figure 1). If baffle is missing, it must be installed. The baffle can be seen by looking down between the grille and the radiator.

Inspection Procedure

1. Remove the upper half of the fan shroud.

2. Pull radiator back away from core support to inspect the opening, being careful not to damage radiator. It is not necessary to remove the hoses or cooler lines.

3. Using a tape measure, measure the width of the opening. The opening must be 863.6 mm or 34.0" wide. If the opening is the correct width, reinstall upper half of shroud. If the opening is not the correct width, use the following procedure.

Repair Procedure

1. Remove radiator using procedures in Section 6B Engine Cooling of the 1988 C/K Service manual.

2. Mark the sections of the core support to be removed (see Figure 1) and remove the sections, using a suitable tool (panel cutter, die grinder with cut-off wheel, panel knibler, etc.). The core support openings are stamped and can be used as a guide. When cutting the lower corners, it is important to leave a small triangle shaped section for proper radiator support rod attachment. The edge of the new opening must be painted to prevent corrosion. Use P/N 1052820 paint or equivalent.

3. Reinstall the radiator and refill the cooling system and road test the vehicle.

For core support modification on vehicles under warranty use:

Labor Op: T7685

Labor Time: Inspect for proper core support opening

6.21 Diesel .4hr 7.4L Gas .3hr

If necessary to modify core support add: 6.2L Diesel .8hr 7.4L Gas .6hr

If equipped with engine oil cooler add: .1 hr If equipped with trans oil cooler add: .7 hr

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.