Attention! Do not remove the radiator cap, drain the fluid, or disassemble the thermostat until the engine is completely cool.
Examination
1. Before checking the thermostat, check the coolant level (see chapter 1), alternator belt tension (see chapter 1), as well as the serviceability of the coolant temperature sensor.
2. If the engine warms up too slowly (according to the temperature sensor), probably the cause of the malfunction is that the thermostat does not close. Replace thermostat.
3. If the engine overheats, touch the upper radiator hose with your hand. If the hose is cold and the engine is hot, the cause of the problem is probably that the thermostat is not opening and fluid is not circulating through the radiator. Replace thermostat.
Warning. Do not drive a car without a thermostat. The computer will operate without feedback, which can lead to increased exhaust emissions and reduced fuel efficiency.
4. If the bottom hose is hot, then the thermostat is open. For troubleshooting, see the Troubleshooting section at the beginning of this Guides.
5. A more serious test of the thermostat can be subjected only by removing it from the engine (see below). If the thermostat remains open at room temperature, it is defective and must be replaced.
6. To fully test the thermostat, hang the thermostat on a wire in a container of water. It is better if the container is transparent so that you can observe the behavior of the thermostat during this test. Dip a thermometer with a 100-degree scale into the container.
7. Heat the water in the tank while watching the thermostat and thermometer, neither of which should touch the walls of the tank (pic. 3.7).
8. Note the temperatures at which the thermostat begins to open and opens fully. Compare your results with the values. given in Technical Data at the beginning of this chapter. Usually, the temperature of its full opening is stamped on the thermostat itself. The thermostat must open at least 8.5 mm.
9. If the thermostat does not open or close at the specified temperatures, or if it gets stuck in some middle position, replace it.
Replacement
10. Disconnect the negative cable from the battery.
Caution: If your car's audio system is equipped with an anti-theft protection, make sure you know the unlock code before disconnecting the battery.
11. Drain the coolant from the radiator (see chapter 1). On a V-engine, remove the air intake duct.
12. Disconnect the hose from the thermostat cover, unscrew the cover bolts (pic. 3.12,a,6).
13. Remove the thermostat cover. Be prepared to spill some coolant.
14. Remove the thermostat, noting its location in the cylinder block.
15. Thoroughly clean mating surfaces. Install a new O-ring to the thermostat.
16. Install the thermostat with the spring inward and align the tab on the thermostat with the cutout in the housing (pic. 3.16).
17. The rest of the steps are performed in the reverse order of removal. Tighten the thermostat mounting bolts to the required torque. Pour in the coolant, start the engine and check for leaks and that the cooling system is in good condition.