When the engine temperature is too high, many people's first reaction is: the thermostat is faulty, quickly remove the thermostat! But is this really reasonable? Today, I will talk to you about whether the thermostat can be removed casually.

( Perkins Thermostat SE573/1)

　　How the thermostat works

　　Currently, most diesel engines use wax-type thermostats with stable performance. When the coolant temperature is below the rated temperature, the thermostat valve closes, and the coolant only circulates in a small loop within the diesel engine, without passing through the radiator for a large loop. This is to accelerate the rise of the coolant temperature, shorten the warm-up time, and reduce the engine's running time at low temperatures.

　　When the coolant temperature reaches the thermostat valve opening temperature, as the engine temperature gradually rises, the thermostat valve gradually opens, allowing more coolant to participate in the large circulation cooling, increasing the heat dissipation capacity.

　　Once the temperature reaches or exceeds the full opening temperature of the main valve, the main valve fully opens, while the auxiliary valve closes the small circulation channel. At this time, the heat dissipation capacity is maximized, ensuring the diesel engine operates within the optimal temperature range.

　　Can the engine run without the thermostat?

　　Do not casually remove the thermostat to run the engine. When the diesel engine water temperature is found to be too high, first carefully check whether the cooling system has issues such as a damaged thermostat or excessive scale in the radiator causing the high temperature. Do not assume the thermostat is hindering coolant circulation based on feeling alone.

(Image from the internet)

　　Effects of removing the thermostat during operation

　　Excessive fuel consumption

　　After removing the thermostat, the large circulation dominates, and the engine dissipates more heat, leading to more fuel waste. The engine running below normal operating temperature for a long time causes incomplete fuel combustion, further increasing fuel consumption.

　　Increased oil consumption

　　When the engine runs below normal operating temperature for a long time, incomplete combustion occurs, more carbon black enters the oil, causing the oil viscosity to thicken and sludge to increase.

　　At the same time, water vapor produced by combustion easily condenses with acidic gases, forming weak acids that neutralize the oil, increasing oil consumption. Also, poorly atomized diesel entering the cylinder washes away the oil on the cylinder walls, diluting the oil and increasing wear on the cylinder liner and piston rings.

　　Shortened engine life

　　Due to low temperature, the oil viscosity is high and cannot timely lubricate the diesel engine's friction parts, increasing wear and reducing engine power.

　　Water vapor produced by combustion easily condenses with acidic gases, worsening corrosion of the engine body and shortening engine life.

　　Therefore, running the engine without a thermostat is harmful in every way and offers no benefits.

(Perkins Thermostat 4133L507)

　　Once it is determined that the thermostat has failed, it should be replaced promptly. Otherwise, the diesel engine will operate for a long time at low (or high) temperatures, causing abnormal wear or overheating and resulting in serious accidents.

　　The new thermostat must be inspected and qualified before installation. Never run the diesel engine without a thermostat, as this causes the engine to frequently operate at low temperatures.