APPARENT COOLANT LEAKS AT THE HEATER CORE

Model and Year: 1988-89 C/K TRUCKS

TO: ALL CHEVROLET DEALERS

Some 1988-89 C/K trucks may experience coolant leaks into the passenger compartment, some of which are being misdiagnosed as heater core leaks. Potential causes of this condition may be insufficient hose clamp pressure and/or incorrect heater hose position.

Repair Procedure

Pressure test the system to 15 psi and visually inspect the position of the heater hoses. If the leak is around the hose clamp, the system may show no pressure loss during this test. Both hoses should be located 3/8" away from the cowl gasket (See Figure 1). If the hoses are pushed up tight against the cowl gasket, there is the potential for coolant leaking past the clamp to enter the passenger compartment.

Condition #1 ------------ If the hoses are located 3/8" away from the cowl gasket, torque hose clamps to 2.2-2.8 Nm and pressure test system to 15 psi.

Condition #2 ------------ If the hoses are not located 3/8" away from the cowl, perform the following service:

1. Cool and depressurize the cooling system.

2. Disconnect both hoses from the heater pipes.

3. Cut off the end of the hoses to remove the area deformed by the hose clamp.

4. Reconnect hoses to heater pipes, leaving 3/8" between the cowl gasket and the end of the hose.

5. Position the hose clamp between the heater pipe bead and the cowl and torque the clamp to 2.2-2.8 Nm.

6. Pressure test system to 15 psi.

For repairs to vehicles under warranty, use the following Labor

Operations and Times:

Condition #1: Labor Op: T7915 Labor Time: .2 Hr

Condition #2: Labor Op: T7916 Labor Time: .5 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.