What Causes Coolant to Boil Over?
3 Answers
The main reason for coolant boiling over is damage to the bottom of the coolant reservoir. Below are the relevant details:1. Introduction: Coolant is used in the cooling systems of automobiles, diesel locomotives, tractors, ships, engines, radiators, and various mechanical equipment such as diesel and gasoline engines. It serves multiple functions including antifreeze, anti-boil, anti-corrosion, and anti-scale protection. Water has a boiling point of 100°C, while high-quality antifreeze coolant typically boils at around 110°C, making it less prone to boiling over than water during summer use.2. Causes: Damage to the coolant reservoir cap, excessively high temperature inside the reservoir. Coolant level exceeding the upper mark on the reservoir. Thermostat malfunction leading to overheating, preventing coolant from circulating through the engine's water passages for major cooling cycle.
Last time I went on a long-distance trip, I encountered coolant boiling over and was sweating with anxiety. This is mostly due to issues with the cooling system, most commonly a clogged radiator or a non-functioning fan. If the radiator surface is covered with insect remains or willow catkins, cold air can't get in, and the water temperature is bound to soar. It could also be a stuck thermostat that won't open, causing the coolant to keep circulating in a small loop without cooling. Those who have topped up with water should pay attention to the concentration—my friend cheaped out and mixed it with tap water, resulting in scale buildup that clogged the pipes like sausages. Rusted water pump blades can also lead to poor circulation; if the hose feels cold, there's definitely a problem. If you smell a sweet odor, check the cylinder head gasket immediately—milky oil indicates oil-water mixing. If you notice boiling over, remember to park in the shade and let it idle to cool down, and never force open a scalding radiator cap!
Veteran driver teaches you a few tricks: If the coolant boils and overflows, it's 80% due to insufficient cooling efficiency. When the weather is hot and the load is heavy, a clogged radiator is the main culprit. Use a flashlight to check the gaps between the cooling fins; if clogged, use an air gun to blow them out. The most common reason for an electric fan not working is a blown fuse—test it by forcing the fan to start with the AC on. Soft and swollen hoses indicate pressure buildup, so check the cylinder head gasket's sealing. Coolant must be replaced every five years, as degraded coolant can corrode aluminum radiators. For modified cars, check if the turbo piping is pressing against the coolant hoses. If you see the red temperature warning light on the highway, don’t hesitate—turn on hazard lights, pull over to the hard shoulder, set the heater to maximum to aid cooling, and keep the engine idling while waiting for rescue.
