How to Determine if a Thermostat is Good or Bad?
4 Answers
Methods to determine the condition of a thermostat are as follows: 1. When the engine starts cold operation, if there is still coolant flowing out from the upper water chamber inlet pipe 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 from the upper water chamber inlet pipe of the radiator, it indicates that the main valve of the thermostat cannot open normally, and repairs are needed at this time. The inspection of the thermostat can be performed on the vehicle, and the methods are as follows: 1. First, observe whether the coolant is sufficient. 2. Check the water flow rate after the engine starts. 3. After the water temperature rises, check the changes in water flow rate and temperature.
As a seasoned driver with over 30 years of experience, I primarily rely on changes in the temperature gauge to assess the thermostat's condition. After starting the engine, the normal coolant temperature should steadily rise to the optimal range (around 90°C) within 5 to 10 minutes. If the gauge suddenly spikes then drops, or remains stuck at low temperatures, it usually indicates a stuck thermostat. Another method is touching the hood - if it feels scalding hot while the dashboard shows low readings, that's a red flag. I've also encountered situations where the cooling fan runs nonstop, signaling cooling system malfunctions. Untreated engine overheating can cause cylinder scoring (expensive repairs) and sometimes increased fuel consumption. I recommend checking the temperature gauge during car washes and visiting your trusted mechanic immediately if abnormalities occur - early intervention prevents major damage.
The temperature gauge on my small car has been fluctuating lately, and after checking, I found out it's a thermostat issue. Judging whether it's good or bad is actually quite simple: observe the coolant temperature changes after starting the car. If the temperature rises too quickly or doesn't move for a long time, you should suspect the thermostat. I usually warm up the car and then stop to see if the fan frequently starts or doesn't respond at all, which often indicates an abnormal thermostat operation. Also, check the engine compartment for any unusual smells or signs of coolant leakage. A faulty thermostat not only causes temperature fluctuations but also makes the air conditioning less effective, which is particularly uncomfortable in summer. Last time, I almost broke down on the highway because I ignored this issue, but luckily I stopped in time to let it cool down. Now, I've bought a Bluetooth OBD scanner on Taobao to monitor real-time data, which is very convenient. New car owners might want to try this to avoid trouble.
When driving daily, I focus on the temperature gauge on the dashboard to determine if the thermostat is faulty. After a normal start, the temperature gauge should steadily rise to the middle zone. If it fluctuates frequently or consistently stays at the low end, it may indicate that the thermostat is stuck and unable to open. Gently touching the pipes near the radiator can also help sense temperature changes. Abnormal temperatures not only affect the driving experience but can also cause the car to consume more fuel or fail to cool properly. I’ve tried using a mobile app to scan for trouble codes for confirmation. If the issue is minor, I handle it myself; if serious, I consult a technician. Remember to regularly check the coolant level to keep the car in good condition and avoid emergencies.
