The radiator is one of the main working components in the engine's water cooling system. After long-term use, the core tubes of the radiator may become blocked and coolant may leak, causing the engine temperature to rise and affecting the normal operation of the engine. Therefore, we need to learn how to check and troubleshoot its faults.

(Perkins 1206F-E70TTA Engine)

　　Radiator Core Tube Blockage

　　When the engine is at low speed, the coolant temperature is normal, but after reaching high speed, the coolant temperature rises sharply. At this time, the radiator should be checked for blockage. Causes of radiator blockage include impurities in the original coolant and mixing different brands of coolant, which produces white crystals that easily block the narrow water channels in the radiator, obstructing the cooling system circulation and causing the engine coolant temperature to be too high.

　　1. Radiator Blockage Fault Inspection

　　a. Measure the temperature difference between the radiator inlet and outlet pipes: Use an infrared thermometer to check if the engine radiator coolant passage is blocked. The temperature at the radiator outlet is the engine coolant temperature, and the return pipe is the temperature of the cooled coolant, which should be about 30°C lower than the outlet temperature. If the return pipe temperature is too low, it indicates radiator blockage and coolant circulation has stopped.

　　b. Observe the coolant flow in the overflow pipe: After the engine reaches the thermostat opening temperature when hot, one person presses the accelerator pedal while another observes the coolant flow in the overflow pipe. If a large amount of coolant flows out of the overflow pipe during rapid acceleration, it indicates severe radiator blockage, causing increased resistance to coolant flow and preventing timely circulation. Blockage in the radiator coolant passage will cause the engine operating temperature to be too high and the radiator must be cleaned.

　　c. If there is inspection space: Use an infrared thermometer to check the radiator surface temperature. If the middle of the radiator is hot and the surrounding area is cool, it indicates blockage in the lower radiator water pipe and the radiator should be cleaned.

　　d. Early wear of the water pump impeller: After the engine reaches normal operating temperature, touch the upper and lower radiator water pipes. If the upper pipe temperature is low, it indicates a thermostat failure and the thermostat should be replaced; if the lower pipe temperature is low, it indicates blockage in the lower radiator water pipe or damage to the plastic impeller of the water pump (modern engines often use plastic water pump impellers, which do not produce abnormal noise when worn). Use an infrared thermometer to check the radiator; if the middle is hot and the edges are cool, it indicates blockage in the lower radiator water pipe and the radiator should be cleaned. If the temperature is uniform, the blockage is not in the lower pipe but the fault is in the water pump impeller, which should be replaced promptly. Many vehicle models require replacing the water pump impeller along with the timing belt and tensioner.

　　e. Chemical reactions can corrode radiator water pipes, causing the upper radiator water pipe to become too soft. Electrochemical reactions occur due to displacement between the antifreeze in the coolant and the pipe material. If a grounding path forms at the boundary between the coolant and pipe, it can accelerate corrosion of the hose. Sliding a finger along the hose to find soft spots indicates corrosion at those points.

　　Connect the negative lead of a digital multimeter to ground and the positive lead to the coolant. If the voltage is greater than 0.3 V, check the ground connection. Poor grounding causes the grounding circuit to use the coolant as a grounding path, accelerating corrosion of the radiator water pipes.

　　The upper radiator water pipe must maintain a certain hardness. If the hose is too soft, it will be sucked flat at high speed, increasing water flow resistance and obstructing coolant circulation.

　　2. Troubleshooting Methods

　　Chemical cleaning: Preparation of cleaning solution. The first type is 750 g of caustic soda (sodium hydroxide) added to 10 L of water, then 250 g of kerosene is added; the second type is 700–1000 g of caustic soda added to 10 L of water, then 150 g of kerosene is added. The first cleaning solution is more corrosive and used for heavily scaled cooling systems, while the second is less corrosive and suitable for lightly scaled systems.

　　Before cleaning, drain the existing coolant, remove the thermostat, then add the cleaning solution. Start the engine and run at medium speed for 5–10 minutes, then stop for 12 hours (or work one shift). Restart the engine, varying the speed to create water impact that suspends scale and other deposits. After running for 10–15 minutes, stop and drain the cleaning solution while still warm. After the engine cools slightly, add clean water and run at medium speed for 4–5 minutes to circulate the water. Repeat this 2–3 times, checking the drained water until it is clean. Finally, reinstall the thermostat and fill with clean coolant.

　　Radiator Water Leakage

　　01

　　How to check?

　　Leakage often occurs at the four corners and the outer tube core.

　　a. Water filling method: During inspection, pour hot water into the radiator and observe leakage marks at damaged parts. This method is convenient but may not detect internal leaks from micro-cracks in the tube core.

　　b. Air pressure method: Use an air compressor or pump for inspection, which can be done at basic repair shops. Connect the radiator to the upper and lower water tanks (or use a special sealing cover), immerse it in water, and pressurize the radiator with air through a hose. Observe if bubbles escape from the radiator. The air pressure should be 1–2 atmospheres for at least 1 minute. After checking one side, flip the radiator to check the other side.

　　02

　　Leakage Fault Repair

　　Depending on the location and severity of the core tube leakage, different repair methods can be used, and the radiator core tubes replaced if necessary. If the number of leaking core tubes does not exceed about 10% of the total, blocking the leaking tubes can be used for repair. If the number exceeds 15%, this method should not be used to avoid reducing the cooling system's effectiveness. Instead, soldering can be used to repair individual leaking spots on the core tubes.