If the engine of a VAZ 2109 car began to overheat when driving or, conversely, it takes too long to warm up before reaching the operating temperature, first of all, it is necessary to check the correct operation of the thermostat.
The thermostat in a VAZ 2109 car is the most important element of the cooling system, which, with the help of a valve, regulates the flow of coolant and ensures that the car warms up, timely removal of excess heat from heating parts and protects the engine from overheating.
Diagnostics of the thermostat at home
For a home check of the thermostat of a VAZ 2109 car, preliminary dismantling of the part from the engine is required. All work must be carried out on an unheated car, because there is a risk of severe burns. Before removing the thermostat, it is necessary to dismantle the crankcase protection and completely drain the antifreeze from the cooling system - after completing the diagnostic work, it can be reused. To drain the antifreeze, you must first open the cap of the expansion tank, and then substitute a previously prepared container for draining the fluid under the cylinder block. Open the drain plug and drain the antifreeze. Then substitute the container under the radiator drain hole and, by unscrewing the plug on it, drain all the coolant.
After draining the antifreeze, loosen the tightening of the clamps and disconnect several pipes from the thermostat housing: the hose from the expansion tank, the outlet hose from the radiator, the hose from the pump pipe, the hose connecting the thermostat to the engine. Carefully removing the thermostat, first of all, the main valve of the part is subjected to visual diagnostics: it can jam in the open position, which causes malfunctions in the operation of the thermostat.
If the valve is closed, then diagnostics of the VAZ 2109 thermostat operation is carried out using a slowly heated container with water. The thermostat is immersed in a container together with a thermometer and, gradually heating the water, the moment when the valve starts to work and the temperature level of this moment are set.
The normal operating temperature of the VAZ 2109 car thermostat is 87 degrees Celsius, an error level of no more than 2-3 degrees is allowed. A properly working thermostat will gradually open the valve as the temperature of the liquid rises, allowing some of the water to pass through the main pipe. When the temperature reaches 108-110 degrees, the thermostat valve should open completely and discharge the heated water into the radiator circuit. As it cools, the thermostat removed from the water should completely close the valve.
Diagnostics of the thermostat directly on the car
The thermostat check on the car is carried out with a cold engine. After starting the engine, it is necessary to check the outlet pipe from the radiator by touch. The norm is the lack of heating of the pipe until the coolant temperature sensor on the instrument panel shows warming up to 80-90 degrees.
If the pipe heats up earlier than this time, it can be assumed that the valve is not working correctly, which leads to an increase in the engine warm-up time and a significant increase in fuel consumption. If the pipe continues to remain cold at high temperatures of the coolant, then the reason may lie in a jammed valve. In this case, replace the thermostat as soon as possible.
