The thermostat controls the flow of coolant through the system and is housed in a housing and mounted on the front of the cylinder head
To ensure rapid heating and temperature regulation, the thermostat partially or completely blocks the flow of coolant circulation through the radiator.
After the engine warms up, the thermostat opens. This allows the coolant to flow through the radiator and release heat into the surrounding space.
The elastic ball in the thermostat is hermetically sealed in a metal housing. It expands when heated and contracts when cooled.
Checking the Thermostat
1. Remove the thermostat.
2. Make sure that the valve spring is tightly compressed when the thermostat housing is completely closed. If the spring is not tightly compressed, replace the thermostat.
3. Place the thermostat and thermometer in a container with a 50/50 solution of ethylene glycol and water. Do not allow the thermostat and thermometer to rest on the bottom of the container, as uneven heat distribution across the bottom may cause inaccurate temperature readings.
4. Heat the solution.
5. Monitor the temperature of the solution during heating.
The thermostat should start opening at 87°C and should fully open at 102°C. If it doesn't open at these temperatures, replace the thermostat.
Removal the thermostat
Caution: Before removing the expansion tank cap, wait until the engine has cooled down to prevent the release of hot fluid or steam.
1. Drain the coolant.
2. Remove the rear part of the timing belt cover
3. Loosen the hose clamp on the upper radiator hose at the thermostat housing.
4. Disconnect the upper hose from the radiator.
5. Unscrew the screws securing the thermostat housing to the cylinder head.
6. Remove the thermostat housing from the cylinder head.
7. Remove the thermostat from its seat in the cylinder head.
8. Inspect the valve seat for foreign objects that could cause it to not close tightly.
9. Check that the thermostat is working properly.
10. Clean the thermostat housing and mating surfaces of the cylinder head.
Installing a thermostat
1. Install the thermostat into the mounting location.
2. Install the thermostat housing.
3. Secure the thermostat housing by tightening the mounting screws to a torque of 20 Nm.
4. Install the removed elements in the reverse order of removal.
[The original article is on the website ChevyMan.ru]