To check the thermostat on a car, start a cold engine and touch the upper radiator hose with your hand - it should be cold. After the coolant temperature reaches (80±1,5) °C, the hose should heat up quickly, indicating the start of fluid circulation in the large circuit. If this does not happen, remove the thermostat and check its operation.
You will need: socket head TORX E10, sliding pliers.
1. Disconnect the wire from the terminal «minus» battery.
2. Drain the liquid from the engine cooling system (see Coolant replacement).
3. Squeeze the retainer of the wiring harness block of the coolant temperature sensor..
4.... and disconnect the block from the sensor.
5. Loosen the radiator hose clamp by squeezing its bent ears with pliers, slide the clamp along the hose..
6.... and disconnect the hose from the nozzle of the thermostat housing
7. Turn out four bolts of fastening of the case of the thermostat to its module …
Note. For clarity, shown on the removed cylinder head.
8.... and remove the housing assembly with the thermostat.
Note. The thermostat and its housing are a difficult to disassemble assembly. When you try to remove the thermostat from the housing, the thermostat mounting posts may break off, so replace the thermostat assembly with the housing.
If you are installing the old thermostat, pry off its rubber seal with a screwdriver..
... remove it from the groove of the housing flange..
... and install a new gasket in the groove. If the new thermostat housing does not have a gasket, install a new gasket as well. The old crimped gasket, when reinstalled, may not ensure the tightness of the connection.
9. To check, lower the thermostat into a container of water heated to 75-78°C. Gradually heating the water, monitor the temperature at which the thermostat valve opens.
Note. The cooling system thermostat is considered serviceable under the following conditions:
- valve opening temperature (80±1,5) °C;
- valve full opening temperature – 95°С;
- valve stroke (size difference A fully open and fully closed valve) - 8.0 mm.
If the thermostat valve does not start to open at 90°C, then the thermostat is defective and must be replaced.
10. Install the parts in the reverse order of removal.
11. Fill with coolant (see Coolant replacement).
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