REMOVAL & INSTALLATION
See Figures 1, 2, 3, 4, 5, 6, 7 and 8
Drain the engine coolant into a clean container so that the level is below the thermostat housing.
When draining the coolant, keep in mind that cats and dogs are attracted by the ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain the coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.
Disconnect the upper radiator hose at the water outlet.
Loosen the two securing nuts and remove the water outlet, gasket, and the thermostat from the thermostat housing.
When installing the thermostat always use a new gasket with sealer and make sure the thermostat spring is facing the inside of the engine. The factory installed thermostat opening temperature is 180°F (82°C) for trucks sold in the U.S., 190°F (88°C) for trucks sold in Canada.
Fig. Fig. 1: Thermostat removal-L16, L18 and L20B engines
Fig. Fig. 2: Thermostat removal-Z20, Z22, Z24 and Z24i engines
Fig. Fig. 3: Thermostat removal-VG30i engines
Fig. Fig. 4: Thermostat removal-SD22 and SD25 engines
Fig. Fig. 5: Removing the water hose from thermostat housing
Fig. Fig. 6: Removing the thermostat housing
Fig. Fig. 7: Removing the thermostat
Fig. Fig. 8: View of the electrical connection for water temperature sending unit