Contents: Examination ⇓ Replacement ⇓
Caution! Do not remove the radiator cap, drain the coolant, or disassemble the thermostat until the engine has completely cooled down.
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 readings), the problem is probably caused by the thermostat not closing. Replace the thermostat.
3. If the engine is overheating, touch the upper radiator hose with your hand. If the hose is cold and the engine is hot, the problem is likely due to the thermostat not opening and fluid not circulating through the radiator. Replace the thermostat.
Warning. Do not drive your car without a thermostat. The computer will operate without feedback, which may result in increased exhaust emissions and decreased fuel economy.
4. If the bottom hose is hot, the thermostat is open. To locate and correct the problem, please refer to the Troubleshooting section at the beginning of this Manuals.
5. A more thorough inspection of the thermostat is possible only after removing it from the engine (see below). If the thermostat remains open at room temperature, it is faulty 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. Place a thermometer with a 100-degree scale into the container.
7. Heat the water in the container, observing the thermostat and the thermometer. Neither of them should touch the walls of the container (figure 3.7).
8. Note the temperature values at which the thermostat begins to open and opens fully. Compare the obtained results with the values. given in Technical data at the beginning of this chapter. Usually the thermostat itself has a stamped temperature value indicating its full opening temperature. The thermostat must open at least 8.5 mm.
9. If the thermostat does not open or close at the specified temperature, or if it gets stuck in some middle position, replace it.
Replacement
10. Disconnect the negative cable from the battery.
Caution: If your vehicle's audio system is equipped with anti-theft protection, make sure you have 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 (figure 3.12,a,6).
13. Remove the thermostat cover. Be prepared for some coolant to spill when doing this.
14. Remove the thermostat, noting its location in the cylinder block.
15. Clean the mating surfaces thoroughly. Install a new O-ring onto the thermostat.
16. Install the thermostat with the spring inward and align the protrusion on the thermostat with the cutout in the housing (figure 3.16).
17. The remaining actions are performed in the reverse order of removal. Tighten the thermostat mounting bolts to the specified torque. Add coolant, start the engine and check for leaks and that the cooling system is in good working order.