Engine Coolant Thermostat Replacement Testing

The coolant thermostat can be tested using a temperature (tempil) stick. The temperature stick is a pencil like device. It has a wax material containing certain chemicals which melt at a given temperature. Temperature sticks can be used to determine a thermostat's operating range, by rubbing 87°C (188°F) and 97°C (206°F) sticks on the thermostat housing. The marks made by the sticks should melt when coolant temperatures of 188°F and 206°F are reached, respectively. These temperatures are the normal operating range of this thermostat, fully opened at 206°F and fully closed below 188°F. Replace the thermostat when it operates outside of this range.

Engine Coolant Thermostat Replacement 4.3L

Caution: Do not remove the radiator cap while the cooling system is hot. Serious personal injury may result. Only remove the radiator cap from a cool engine.

1. Remove the necessary coolant from the radiator. Refer to Draining and Filling Cooling System .
2. Remove the upper radiator inlet hose.



3. Remove the coolant outlet bolts.



4. Remove the coolant outlet from the lower intake manifold.
5. Remove the thermostat gasket.



6. Remove the coolant thermostat.
7. Clean all the sealing surfaces of the coolant outlet.
8. Clean the sealing surface on the lower intake manifold.

1. Install the coolant thermostat in the lower intake manifold.

Important: To prevent leakage, thoroughly clean all parts and sealing surfaces.




2. Install a new gasket (if used). Otherwise, place a 3 mm (1/8 in) bead of RTV sealer (GM P/N 1052289, or equivalent) at the groove on the coolant outlet sealing surface.
3. Install the coolant outlet on the lower intake manifold.



4. Install the attaching bolts.

Tighten
Tighten coolant outlet bolts to 19 N·m (14 lb ft).

Refer to Fastener Tightening Notice in General Information.

5. Install the radiator inlet hose.
6. Fill the cooling system with specified coolant and concentration. Refer to Radiator Replacement .
7. Inspect all sealing surfaces for leaks after starting the engine. Refer to Radiator Leak Testing (On and Off Vehicle) .