Thermostat — replacement
Warning: Wait until the engine is completely cool before beginning this procedure.
1. Disconnect the cable from the negative terminal of the battery (see Engine electrical systems).
2. Drain the cooling system (see Tune-up and routine maintenance).
4.3L V6, 5.3L and 6.2L V8 models
Note: The thermostat and thermostat housing are replaced as a unit on these models.
3. Remove the air intake duct and resonator assembly (see Fuel and exhaust systems).
4. Squeeze the hose clamps and slide them up the hoses, then detach the radiator hose and the expansion tank hose from the thermostat housing cover. If the hose sticks, grasp it near the end with a pair of adjustable pliers and twist it to break the seal, then pull it off. If the hose is old or deteriorated, cut it off and install a new one.
4.4 Detach the expansion tank and radiator hoses from the thermostat housing cover
5. Remove the bolts and detach the thermostat housing/thermostat assembly (see illustration). If the housing is stuck, tap it with a soft-face hammer to jar it loose. Be prepared for some coolant to spill as the gasket seal is broken.
4.5 Thermostat bolt locations — 4.3L V6, 5.3L and 6.2L V8 models
6. Clean the mating surfaces of the coolant manifold and thermostat housing cover.
7. Install a new 0-ring seal to the thermo- stat housing (see illustration).
4.7 Replace the thermostat housing 0 -ring with a new one
8. Install the thermostat/housing to the coolant manifold and install the bolts, tightening them to the torque listed in this Chapter’s Specifications.
9. Reconnect the hoses to the thermostat housing.
10. Refill the cooling system (see Chapter 1).
6.0L V8 models
11. Remove the air intake duct and resonator assembly (see Fuel and exhaust systems).
12. Follow the lower radiator hose to the engine, then disconnect it. If the outer surface of the thermostat housing covers that mate with the hose is deteriorated (corroded, pitted, etc.) it may be damaged further by hose removal. If it is, the thermostat housing cover will have to be replaced.
13. Remove the thermostat housing cover from the engine (see illustration).
4.13 Thermostat housing cover bolts — 6.0L V8 engines
14. Note how it’s installed (which end is facing out), then remove the thermostat.
15. Clean the sealing surfaces on the water pump housing and the thermostat housing cover.
16. Install a new rubber 0-ring around the thermostat (see illustration). Install the thermostat into the coolant manifold, spring-end first.
4.16 Install a new rubber seal around the thermostat
17. Place the thermostat housing onto the coolant manifold and install the bolts. Tighten the bolts to the torque listed in this Chapter’s Specifications.
18. The remainder of installation is the reverse of the removal procedure.
19. Refill the cooling system (see Tune-up and routine maintenance).