Contents: Removing the thermostat in… ↳ Installing a thermostat ↳ Removing the thermostat in a diesel… ↳ Installing a thermostat ↳ Checking the Thermostat ↳
The coolant temperature regulator (thermostat) opens the way for the coolant to the radiator as the engine heats up. If the thermostat remains closed due to some defect, the engine overheats. This is determined by the fact that the temperature readings on the dashboard increase, and the radiator remains cold. A defective thermostat can remain open even after the coolant has cooled down. In such a case, the engine will take a very long time to warm up to operating temperature or will not reach it at all, the heating power of the cabin is weak.
Attention! If the engine becomes hot after driving a short distance, this may be due to the radiator being clogged with scale.
Removing the thermostat in 4-cylinder petrol engines
Drain the coolant and collect it, see p. 3.3.
Remove the thick coolant hose from the radiator and the thin hose from the thermostat housing. To do this, use pliers to loosen the fastening spring clamps. If necessary, remove the air intake hose first, as this will provide better access to the thermostat, see p. 5.6.
Disconnect the wire plug from the temperature sensor at the top of the thermostat housing.
Loosen the three mounting bolts and remove the coolant drain pipe along with the sealing ring and temperature regulator.
Installing a thermostat
Check the old thermostat before installing it, see end of chapter.
Clean the sealing surfaces of the coolant drain pipe and thermostat housing.
Install the thermostat with the sealing ring into the housing. A defective seal must be replaced. Install the housing onto the cylinder head and tighten it to a torque of 20 Nm.
Connect the coolant hoses to the thermostat housing and secure them with clamps.
Connect the temperature sensor plug.
Install the air suction hose.
Fill with coolant, see p. 3.3.
Warm up the engine, check the connecting pipes for leaks, they may need to be carefully tightened.
Removing the thermostat in a diesel engine
Drain and collect the coolant, see p. 3.3.
Disconnect the thick coolant hose from the thermostat housing that goes to the radiator. In doing so, use pliers to loosen the fastening clamp.
Disconnect the wire plug from the temperature sensor "1" at the top of the thermostat housing.
Loosen the two mounting bolts "2" and remove the coolant drain pipe together with the sealing ring and thermostat.
Remove the thermostat.
Installing a thermostat
Check the old thermostat before installing it.
Clean the sealing surfaces of the coolant drain pipe and thermostat housing.
Install the thermostat with the sealing ring into the housing. A defective "arrow" seal must be replaced in any case. Install the housing onto the cylinder head and tighten it to 20 Nm.
Connect the coolant hose to the thermostat housing and secure it with a clamp.
Connect the plug to the temperature sensor, it should click into place.
Fill with coolant, see p. 3.3.
Warm up the engine, check the connecting pipes for leaks, they may need to be carefully tightened.
Checking the Thermostat
Slowly heat the thermostat in a vessel with water. The thermostat should not touch either the bottom or the walls of the vessel. The thermostat should be completely covered with water. Check the water temperature with an appropriate thermometer.
At an opening temperature of approximately +85°C (in diesel engines +70°C), the thermostat should begin to open.
When cooling, check if the thermostat closes completely, otherwise replace it.