Pull the whole heater suitcase. You can then clean, lube, and seal everything much easier. If you don't have A/C, it's only an hours job. Put an old blanket down on the carpet to catch any liquid that may spill out the heater core. Start by pulling the glove box insert and the RH kick panel and insulation, then the hook holding the suitcase to the cowl, then the defroster hoses (CAREFULLY as they fall apart just looking at them) then disconnect the cables from the flaps and unplug the wiring for the fan. Pull and plug the heater hoses at the firewall, then just the nuts holding the suitcase to the firewall is all that's left. Pull the assy. out and split it apart on the bench. Lube the clips before removal will help prevent chipping the fiberglass housing.