What Causes Bubbles in the Engine Radiator?
2 Answers
During vehicle operation, water bubbling up from the radiator cap is primarily caused by poor combustion chamber sealing, which allows high-temperature combustion gases from the diesel engine to enter the cooling water cavity. Therefore, to address the issue of water bubbling in the radiator, the combustion chamber sealing problem must first be resolved. The main causes of combustion chamber sealing failure are as follows: 1. Cause one: The cylinder head is warped or deformed, resulting in an uneven bottom surface. 2. Cause two: The top surface of the cylinder block is uneven. 3. Cause three: Insufficient torque on the cylinder head fastening bolts, or the bolts not being tightened evenly in several steps using a symmetrical cross pattern. 4. Cause four: Residual debris in the bolt holes at the top surface of the cylinder block reduces the torque on the cylinder head bolts, leading to a "false tightness" phenomenon. 5. Cause five: The threaded holes for the cylinder head bolts on the cylinder block are not properly tapped or threaded to the required depth.
In the previous car repair case where bubbles were observed in the radiator, the direct cause was engine internal pressure entering the cooling system. In most cases, this happens due to aging cylinder head gaskets, where high-temperature and high-pressure combustion gases squeeze into the coolant through gaps, forming bubbles. If not addressed promptly, the coolant may spray and scald people, and the water temperature could soar, leading to cylinder scoring. First, open the engine hood and check the radiator surface for oil stains or coolant that appears cloudy with a gasoline smell when the engine is cold—these are telltale signs. The safest action is to immediately turn off the engine and call for a tow truck to prevent further damage. Long-term neglect of antifreeze replacement can also reduce sealing performance, so it's recommended to change it every two years. As a driver, if you notice bubbling, don’t hesitate—take the car to a reputable repair shop to check the cylinder head flatness and gasket condition. Addressing minor issues early can save significant repair costs later.
