Unlike some other car units, you can not check the thermostat directly in the store or at the bazaar. But do not be afraid to buy a “pig in a poke” – the law on consumer rights allows you to return the part (or any other product, except for food) to the seller within 14 days after purchase, not only if it is faulty or does not fit you, but even if for some reason you do not like it. And if you have been looking for a long time, where to dispose of an old car, you should contact here: https://towingandscrapcarremoval.ca/scrap-car-removal-newmarket/.
You can check the thermostat at home without installing it on the car. To do this, it is lowered suspended (on a wire or rope) into a pot of cold water, and then the water begins to heat. To control the temperature, a thermometer with a scale of 0-100 oC should be placed in the water. Checking consists in determining the opening temperature of the valve. The thermostats of “Zhiguli”, “Volga”, “Moskvich” the valve should be fully opened at 81-85 oC. The valve of “VW” and “Fords” only starts to open at this temperature. The Opel valve starts to open at 92 oC. Many diesel ones have it at 68-73 oC.
On the car you can check the functionality of the thermostat as follows. Before you start a cold engine, drop a thermometer (with a scale of 0-100 oC) through the filler neck into the radiator. If immediately after starting the engine the coolant temperature did not change much, and then there was a sharp jump in temperature, the thermostat is good. If the temperature of the antifreeze began to rise smoothly immediately after starting the engine, then the thermostat is defective.
The radiator of many foreign cars has no filler neck, so it is impossible to use a thermometer to check it. In this case it is necessary to find an access to the upper radiator tank and check the coolant heating by touch. If the radiator stays cold for a long time after you start the engine and then starts heating up intensively, it means the thermostat is working. If the radiator heats up slowly right after starting the engine, the thermostat is defective.
In general the thermostat lasts long enough. The cause of its accelerated breakdown can be usage of low-quality coolant or its untimely replacement. The lack of anti-corrosion additives in the antifreeze leads to the destruction of the thermostats.