APPARENT COOLANT LEAKS AT THE HEATER CORE

SUBJECT: APPARENT COOLANT LEAKS AT THE HEATER CORE (REPAIR PROCEDURE)

VEHICLES AFFECTED: 1988-89 C/K TRUCKS

Some 1988-1989 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.

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.