How to Check if a Thermostat is Good or Bad?
2 Answers
There are mainly the following methods to check whether a thermostat is good or bad: 1. When the engine starts cold operation, if there is still coolant flowing out at the inlet pipe of the upper water chamber of the radiator, it indicates that the main valve of the thermostat cannot close. 2. When the engine coolant temperature exceeds 70°C, if there is no coolant flowing out at the inlet pipe of the upper water chamber of the radiator, it indicates that the main valve of the thermostat cannot open normally, and repair is needed at this time. The function of the thermostat is to automatically adjust the amount of water entering the radiator according to the temperature of the coolant, change the circulation range of the water, and adjust the heat dissipation capacity of the cooling system to ensure that the engine works within a suitable temperature range. The thermostat must maintain good technical condition, otherwise it will seriously affect the normal operation of the engine. If the main valve of the thermostat opens too late, it will cause the engine to overheat; if the main valve opens too early, it will prolong the engine preheating time and make the engine temperature too low.
Checking the thermostat isn't that hard - I often do this kind of DIY job myself. First, start the engine and let the car run for a few minutes. Normally, the temperature gauge should settle around the middle mark, say 90°C. If the temperature takes forever to rise or you're getting lukewarm air in winter, the thermostat might be stuck open, causing excessive cooling. If the temperature suddenly spikes or triggers an alarm, it's likely the thermostat is stuck closed, leading to overheating. You can remove the thermostat for testing: put it in a pot of cold water and heat it while monitoring with a kitchen thermometer. It should fully open between 80-90°C. If it doesn't open or opens insufficiently, it's time for a replacement. Remember to drain the coolant first to prevent burns, and check hoses for leaks or blockages while you're at it. Unstable coolant temperature not only wastes fuel but also damages engine piston rings - fixing it early saves trouble.
