The thermostat is located inside a housing, which is attached to the front of the cylinder head (2.5L) or to the front of the intake manifold (4.3L).
REMOVAL & INSTALLATION
See Figures 1, 2, 3, 4, 5, 6, 7, 8 and 9
Fig. Fig. 1: Exploded view of the thermostat and housing assembly-2.5L engine
Fig. Fig. 2: Exploded view of the thermostat and housing assembly-carbureted and TBI 4.3L engines
Fig. Fig. 3: If access is difficult with the hose attached ...
Fig. Fig. 4: ... remove the hose, then loosen and remove the housing retainers
Fig. Fig. 5: Once the housing is free, carefully lift it from the engine to expose the thermostat
Fig. Fig. 6: Sometimes, the thermostat will lift from the engine with the housing ...
Fig. Fig. 7: ... but if not, note the direction it is installed, then lift if from the engine for replacement
Fig. Fig. 8: Exploded view of the thermostat and housing assembly-4.3L (1992-95 VIN W) CMFI engine
Fig. Fig. 9: Exploded view of the thermostat and housing assembly-4.3L (1996 VIN W) CSFI engine
Disconnect the negative battery cable for safety.
Place a catch pan under the radiator, open the drain cock and drain the cooling system to a level below the thermostat housing.
When draining the coolant, keep in mind that cats and dogs are attracted by 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.
Remove the thermostat housing-to-engine bolts or bolt and stud, as applicable,
Separate the housing from the cylinder head (2.5L) or manifold (4.3L) and carefully remove the thermostat.
Using a plastic scraper, clean the gasket mounting surfaces.
Except for 1996 vehicles, place a
in. (3mm) bead of RTV sealant in the groove of the water outlet mating surface.
Place the thermostat in position, then install and secure the housing using a new gasket on all but 1996 vehicles.
Tighten the thermostat housing-to-engine bolts or bolt and nut to 21 ft. lbs. (28 Nm) for 1985-94 vehicles, 15 ft. lbs. (20 Nm) for 1995 vehicles or to 18 ft. lbs. (25 Nm) for 1996 vehicles.
Connect the battery cable, the properly refill and bleed the cooling system.
Run the engine and check for leaks.