Attention! Do not open the radiator cap and do not remove the thermostat until the engine has completely cooled down! See also the warning at the beginning of the Section Antifreeze - general information.
Examination
1. Before finally establishing your opinion about the failure of the thermostat, check the coolant level in the system, the condition and tension of the drive belt (see chapter Vehicle settings and routine maintenance), as well as the correct functioning of the temperature meter / control lamp.
2. One of the possible reasons for the engine warming up too slowly (according to meter readings) is the thermostat sticking in the open position. Replace the thermostat with a new one.
3. If the engine overheats, feel the lower radiator hose with your hand. If the hose is not hot, the thermostat may be stuck closed, cutting off coolant circulation through the radiator. Replace thermostat.
Attention! Never operate the vehicle with the thermostat removed, as this may break the feedback of the on-board processor, which will lead to an increase in the toxicity of exhaust gases and an excessive increase in fuel consumption.
4. If the lower hose is hot, this means that the coolant is properly circulating through the radiator, i.e. thermostat is open. Refer to the section on diagnosing problems with the cooling system (see Introduction at the beginning of this manual).
5. The most accurate results are obtained by checking the thermostat on a workbench.
6. Remove the thermostat from the engine (see below).
7. Tie a piece of wire to the thermostat assembly and lower it into a container filled with water. Put the thermometer in there.
Attention! Make sure that the thermometer and thermostat do not come into contact with the walls and bottom of the container.
8. Start slowly heating the water, watching the change in the thermometer readings - the thermostat valve should actuate exactly as required Specifications.
9. Assess the value of the full opening of the valve, the nominal value is 8 mm (refer to accompanying illustration).
Replacement
Details of installing a thermostat on a gasoline engine
1. Disconnect the negative cable from the battery.
Attention! If the stereo system installed in the car is equipped with a security code, before disconnecting the battery, make sure that you have the correct combination to activate the audio system!
2. Drain the coolant (see chapter Vehicle settings and routine maintenance).
3. At the corresponding complete set disconnect vacuum hoses from a thermostat casing.
4a. Separate the thermostat housing from the engine (refer to illustration above), prepare to collect spilled coolant.
4b. The radiator hose, if not in need of replacement, can be left connected to the shroud (refer to accompanying illustration).
5. Remove the thermostat from the casing, try to remember its installation position. Thoroughly clean the sealing surfaces of the cover and thermostat housing with a scraper, then wipe them with a rag soaked in solvent.
6. Install a new rubber seal.
7. Install the thermostat and its casing in their regular places, with the appropriate configuration, make sure that the assembly is turned up with the bleed valve.
8. Tighten all fasteners to the required torque. Reinstall all removed components in reverse order of removal.
9. Fill the cooling system (see chapter Vehicle settings and routine maintenance). Start the engine and check for leaks and the thermostat is functioning properly (see paragraphs 2 to 4, Checking).