Execution sequence
1. We prepare the car for work (see «Preparing the car for maintenance and repair»).
Warning! The coolant level should be checked on a cold engine. A slight increase or decrease in the coolant level when the engine warms up and cools down is not a malfunction. This is due to the thermal change in the volume of the liquid.
2. We check the coolant level in the expansion tank, which should be 25-30 mm above the MIN·mark made on the expansion tank body.
If the fluid level is at or below the MIN·mark, add coolant to the reservoir (see below, «Coolant - replacement»).
Recommendation. If you have to add coolant regularly, you should check the tightness of the cooling system.
3. We check the absence of fluid leaks from the radiator, the engine block, the installation location of the temperature sensor, the connections of the rubber hoses of the cooling system and their integrity.
Recommendation. You can try to eliminate the leakage of coolant from under the hoses by replacing the spring clamps with screw ones. Do not overtighten the clamps, as they may cut the hoses.
4. We check the integrity of the body of the expansion tank, engine radiator and heater.
5. Open the cover of the expansion tank of the cooling system (see above).
6. We collect coolant in the hydrometer so that the float emerges.
7. On the scale of the float, we determine the density of the liquid.
Comment. The hydrometer is a float with a scale graduated in units of density kg/m3. Depending on the density of the liquid, the float will sink to different depths. The scale is applied to the float in such a way that the liquid level is opposite the value corresponding to its density. Antifreeze is sold either in a diluted form, ready for use, or in the form of a concentrate, which must be diluted with distilled water before filling in accordance with the operating temperature of the car. The concentration of antifreeze is determined by its density (see table). Sometimes the scale indicates the range of the minimum allowable temperature.
Table 9.4.3. Density and concentration of antifreeze
Density of antifreeze at 20°C, kg/m3 | The concentration of ethylene glycol in antifreeze,% of the volume | Minimum ambient temperature at which the engine can be operated,°C |
1 050 | 30 | -10 |
1 058 | 35 | -15 |
1 067 | 40 | -20 |
1 074 | 45 | -25 |
1 082 | 50 | -30 |
1 090 | 55 | -35 |
1 098 | 60 | -45 |
Comment. It is necessary to dilute the antifreeze before it is poured into the cooling system, since only in this way can the specified ratios of antifreeze and distilled water be strictly observed. We check the density of antifreeze after mixing.
8. Using the table, by the density of antifreeze, we determine its concentration and the minimum temperature at which it can be operated.
9. If the concentration of antifreeze does not match the climatic zone, we replace the coolant (see below, «Coolant - replacement»).
Comment. Do not try to increase the concentration of ethylene glycol excessively. When it increases above 60%, the freezing point of antifreeze begins to increase again and at 100% ethylene glycol it will be -13°C.
10. We make sure that the cap of the expansion tank is tightly wrapped.
11. We are convinced of the tightness of the thermostat housing and the connection of the coolant pump and the cylinder block.
12. Check for fluid leakage from the pump drain (located at the bottom of the pump), indicating the wear of its gland.
13. To check the thermostat, start a cold engine. We control the temperature and circulation of the coolant in a small and large circle by touch, by changing the temperature of the hoses and pipes of the cooling system (The air filter has been removed for clarity).
Comment. If the engine cooling system is working properly, then when the coolant temperature is less than 90°C, the thermostat valve should be closed, and the coolant should circulate in a small circle. As a result, the lower radiator hose and the radiator itself will be noticeably colder than the thermostat housing, through which hot coolant circulates. When the coolant temperature reaches about 90°C, the thermostat valve will open and a gradually increasing flow of hot liquid will begin to flow into the radiator. In this case, first the radiator, and then its lower hose, will begin to heat up.
14. Leave the engine running until the engine radiator fan is activated. When the coolant temperature rises to a certain value, the electric fan should turn on, and when the temperature drops, it should turn off automatically.
Recommendation. If the electric fan did not turn on in time, the liquid boiled, it is necessary to check the fan motor or the engine control system for proper operation.
Recommendation. Checking the coolant temperature sensor is shown in the section «Coolant temperature sensor - check and replace».