1999 Other GMC Models Heater Core

Removal & Installation ("C" & "K" Series) Disable air bag system. See AIR BAG SYSTEM SAFETY article in GENERAL INFORMATION. Disconnect negative battery cable. Remove glove box by squeezing sides together. Remove 2 instrument panel retaining bolts from glove box opening. Remove center floor duct. Remove center support bolt. Remove Electronic Control Module (ECM) and tray. Remove both kick panels. Remove blower motor cover and blower motor. Remove driver's lower instrument panel cover and knee bolster. Lower steering column. Remove instrument panel left and right pivot bolts located at lower corners of instrument panel. Remove 3 screws from defrost vent, near windshield. Disconnect any connectors and tilt instrument panel back far enough to access heater case. Remove coolant recovery reservoir from engine compartment. Drain engine coolant. Disconnect heater hoses at core. Remove bolts and nuts from engine compartment attaching heater case to vehicle. Remove heater case. Remove 7 screws attaching heater case cover plate. Remove screws and bracket attaching core to case. See Fig. 6 . Remove heater core. To install, reverse removal procedure. Replace any seals. Fill cooling system. Start engine and check for leaks.