What are the effects of removing a car thermostat?

[JayceLee]

Removing the car thermostat will prevent the car from sensing temperature during cold starts, resulting in cold engine starts and accelerated engine wear. Here is some information about car thermostats: Purpose of installation: To allow the engine to reach its optimal operating state as quickly as possible, reduce engine wear, improve fuel atomization, and at the same time increase the heating speed of the car's interior. Function: To control the circulation of coolant between the engine and the radiator. When the coolant temperature is relatively low, the thermostat remains closed, allowing only the coolant within the engine to heat up. This is referred to as a "small circulation." When the coolant in the engine reaches a certain temperature, the thermostat automatically opens to connect with the radiator, which is then referred to as a "large circulation."

[Mary]

With over a decade of car repair experience, I've seen numerous cases where people removed the thermostat to cool down their engines, only to make things worse. Without a thermostat, the engine warms up as slowly as a snail, and in winter, the heater takes over half an hour to get warm. More critically, the engine constantly operates at low temperatures, leading to rapid carbon buildup, a direct 10% spike in fuel consumption, and easily exceeding emission standards. The biggest issue is that excessive coolant flow reduces cooling efficiency, causing localized overheating in the cylinder block, which can lead to cylinder scoring. Last year, I repaired a Camry with its thermostat removed—the cylinder head was warped, costing over 8,000 yuan to fix. I strongly advise against removing it; replacing a new thermostat only costs around 200 yuan.

[DiLevi]

Veteran truck drivers with twenty years of experience all know that removing the thermostat turns your vehicle into a gas guzzler. My old Jiefang truck had its thermostat removed, and in winter, the temperature gauge just wouldn't reach the midline, while the fuel consumption display showed two notches higher than normal. It wasn't until a mechanic explained it to me that I understood: when the engine temperature is too low, the ECU drastically enriches the fuel mixture, leading to incomplete combustion and black water dripping from the exhaust pipe. While lack of cabin heat might be tolerable, accelerated piston ring wear is what really kills the engine—mine started burning oil in less than three years. Now, whenever I see roadside mechanics recommending thermostat removal, I always advise new drivers to steer clear of such advice.

[McBennett]

During the -30°C winter in Northeast China, I tried removing the thermostat. As a result, I had to warm up the car for an extra ten minutes before commuting every day. When the coolant temperature couldn't rise, I didn't dare exceed 2000 RPM, making overtaking nerve-wracking. The most frustrating part was the AC vents blowing air below 40°C, with painfully slow windshield defogging. On highways, it was even worse - the temperature gauge needle kept wobbling in the cold zone while the radiator fan cycled frequently. After three miserable months, I promptly reinstalled a new thermostat. The fuel savings weren't even enough to cover the cost of antifreeze.

[ZaneDella]

You might not know that removing the thermostat can affect emissions testing. The three-way catalytic converter only becomes effective above 80°C. Without a thermostat, the temperature in the front section of the exhaust pipe remains too low, causing exhaust pollutant levels to exceed standards by three to four times. Last week, I helped my neighbor with their annual inspection, and it failed—the CO level skyrocketed to 6.8%. After installing an aftermarket thermostat and retesting, the readings were within limits. Running the engine at low temperatures for extended periods can also lead to oxygen sensor poisoning, and replacing an oxygen sensor costs over 600 yuan.

[OAaliyah]

Among the cooling tricks circulating in the modification community, removing the thermostat is the most deceptive. Actual tests show that without it, coolant temperature rises faster at medium and low speeds, and can spike to 105°C in traffic jams. This happens because the coolant flows too quickly, leaving the radiator insufficient time to dissipate heat. During a track day, I once witnessed a fellow enthusiast's turbocharged car burst a coolant hose, with remnants of the removed thermostat base clogging the water passage. The proper approach is to upgrade to a high-flow water pump paired with an improved thermostat—every component in the OEM system serves a purpose.