5.1.4. Check of the thermostat

Check without removal of the thermostat


  1. Before removing and checking operability of the thermostat, be convinced that problems with cooling of the engine arose not owing to insufficient amount of cooling liquid or a weak tension of a driving belt. Be convinced of serviceability of the indicator located on a combination of devices.
  2. If the engine long gets warm up to the working temperature (according to indications of the indicator), the thermostat, perhaps, is jammed in open situation. In this case the thermostat should be replaced.
  3. On the other hand, long warming up can be a consequence of lack of the thermostat. It could be made specially or inadvertently (forgot to establish after repair). Do not use the car without thermostat. The control system of the engine will longer support the mode of warming up of the unit in which the engine consumes more fuel, and the fulfilled gases contain bigger amount of harmful impurity.
  4. If the engine overheats, touch the top hose of a radiator. If it not hot, but the engine is overheated, the thermostat, perhaps, jammed in a closed position. Liquid does not get to a radiator and circulates on a small circle. In this case replace the thermostat.
  5. If the top hose of a radiator hot, it means that the thermostat is open and liquid normally circulates on system, - study the recommendations provided in the Section Diagnostics of Malfunctions.

Check with removal of the thermostat

Check of serviceability of functioning of the thermostat

1 — the Thermostat

2 — the Dish-shaped valve


  1. Remove the thermostat (see the Section Removal and installation of the thermostat).
  2. If the thermostat at the room temperature is abroach - it is faulty and is subject to replacement.
  3. For rough check of operability of the thermostat suspend it on a piece of a twine in the container with water. The thermostat should not concern capacity walls. Begin to heat capacity.

From the moment of achievement with the temperature of value at 8 °C points of the beginning of opening of the valve are lower the speed of heating has to make no more than 1-2 °C/min.

  1. In process of water heating the thermostat has to open (it occurs just before water boiling). As temperature of boiling of water makes 100 °C, the thermostat can not open completely (see Specifications). Take the thermostat and let's it cool down, - the valve has to be closed completely.
  2. If the thermostat does not open when heating or is not closed when cooling, replace it.
  3. At installation of the thermostat pay attention to the next moments:
  1. Track that the interfaced surfaces were smoothed carefully out, do not forget to prepare and establish a new sealing ring;
  2. Track correctness of orientation of the thermostat in a casing;
  3. Track that bolts of fastening of a cover were tightened with the required effort (see Specifications);
  4. Begin gas station of the cooling system (see the Head the Current leaving and service) only having made sure of correctness of connection of all hoses;
  5. Upon completion of installation start the engine, warm up up to the normal working temperature and make sure of lack of signs of development of leaks.