How to change thermostat on 2002 envoy?

Answer 1

Removal & Installation

4.2L Engine

1. Remove the necessary coolant from the radiator.
2. Remove the alternator, as outlined in the Engine Electrical Section.
3. Loosen the outlet hose clamp at the thermostat housing. Remove the outlet hose from the thermostat housing.
4. Remove the thermostat housing bolts.
5. Remove the thermostat housing from the engine block.
6. Clean all of the surfaces of the thermostat housing.
7. Clean the sealing surface of the engine block.

To install:

Fig. Thermostat mounting-4.2L engine

1. Install the thermostat housing to the engine block.
2. Install the thermostat housing bolts and tighten to 89 inch lbs. (10 Nm).
3. Lubricate the inner diameter of the radiator hose with engine coolant.
4. Install the outlet hose to the thermostat housing. Secure the hose with the clamp.
5. Install the alternator.
6. Fill the cooling system with specified coolant and concentration.
7. Inspect all sealing surfaces for leaks after starting the engine.

4.3L Engine

The thermostat is located between the water outlet and a housing built into the intake manifold.

CAUTION

Never open, service or drain the radiator or cooling system when hot; serious burns can occur from the steam and hot coolant. Also, when draining engine coolant, keep in mind that cats and dogs are attracted to ethylene glycol antifreeze and could drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantities. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or is several years old.

1. Disconnect the negative battery cable.
2. Remove the air inlet duct.
3. Drain the cooling system to a level below the thermostat.
4. Remove the thermostat outlet-to-engine retainers (usually either 2 bolts or 1 bolt and 1 stud), then remove outlet from the intake manifold.
5. Remove the thermostat from the housing, noting the orientation for installation purposes.

   Fig. Unfasten the thermostat outlet-to-engine bolts

   Fig. Remove the outlet from the intake manifold

   Fig. Remove the thermostat from the housing

To install:

1. Carefully clean the all traces of the old gasket or sealer from the housing and outlet.
2. Install the thermostat to the housing, oriented as noted during removal, then position a new gasket (if used).
3. Place a 1 / 8 in. bead of RTV sealant in the groove on the water outlet sealing surface, then install the outlet while the sealer is still wet.
4. Install the outlet retainers and tighten to 14 ft. lbs. (19 Nm).
5. Properly fill the engine cooling system and check for leaks.
6. Install the air inlet duct.

5.3L Engine

NOTE

The thermostat is not serviceable separately. The water pump inlet and thermostat must be replaced as an assembly.

1. Drain the cooling system to a level below the thermostat.
2. Remove the radiator outlet hose.
3. Remove the water pump inlet bolts.
4. Remove the water pump inlet and thermostat from the water pump.

To install:

1. Install the thermostat and thermostat housing to the water pump.
2. Install the thermostat housing bolts. Tighten the bolts to 11 ft. lbs. (15 Nm).
3. Install the radiator outlet hose.
4. Properly fill the engine cooling system and check for leaks.