What Causes Engine Overheating and Loss of Coolant?

[VanJeffrey]

First, check if there are any leaks in the cooling system. Second, verify whether the engine cooling system's heat dissipation is functioning properly. Reasons for Coolant Spraying Out: It may be due to the quality of the coolant. Mixed alcohol or methanol-based coolants have a low boiling point, making them prone to boiling over and spraying out. If the coolant's foaming tendency does not meet standards, even if it doesn't boil over, it can accumulate a large amount of foam during circulation, leading to coolant spraying out. Functions of Automotive Coolant: Coolant is essentially the water in the car's radiator, but it is used to replace ordinary tap water. It has a high boiling point, typically around 120°C, and a freezing point that can reach -40°C to -60°C. This effectively prevents the vehicle from overheating and also protects the radiator or cooling system from damage caused by freezing in winter.

[JourneyAnn]

A few days ago, while helping a neighbor check their car, I encountered this exact situation—the coolant level had mysteriously dropped significantly. The most common cause is a leak in the cooling system, so focus on inspecting the radiator, hose connections, and the water pump’s sealing ring. Older cars, in particular, are prone to rubber hose degradation and seepage, sometimes leaking when hot but not when cold. A faulty pressure valve in the radiator cap is another hidden issue, as it can cause fluid to be forced into the overflow tank and spill out at high temperatures. If you notice a sweet smell while driving or spot colored puddles under the car, it’s likely an external leak. Additionally, coolant has a higher boiling point than water, so using water as a substitute will lead to earlier boiling and loss. Don’t wait until the temperature gauge spikes—get to a repair shop for a pressure test right away.

[Almeida]

Car enthusiasts who have experienced coolant loss can surely relate to this panic. Beyond leakage issues, one must consider the possibility of internal leaks. For instance, a blown cylinder head gasket may manifest as emulsified engine oil (milky white foam on the oil cap) or white smoke from the exhaust pipe. Burning coolant is more troublesome than leakage, often requiring engine disassembly for repair. The design of the overflow tank is also crucial—some vehicles fail to draw coolant back into the main radiator during cooldown, resulting in naturally low fluid levels. Additionally, internal leaks in the intercooler of turbocharged cars can occur, though this is relatively rare. As a side note, avoid mixing different antifreeze formulations, as incompatible chemicals can form deposits that clog cooling passages.

[McBrady]

Last month, my old car just experienced this issue. Upon opening the hood, I found the coolant reservoir empty, while the temperature gauge soared into the red zone. After careful inspection, it turned out to be a stuck thermostat causing a blockage in the small circulation loop, leading to intense evaporation due to high temperatures. Radiator fins clogged with insect remains and dust can also reduce cooling efficiency, eventually causing coolant overflow and consumption. Corrosion of the water pump impeller can result in insufficient coolant circulation. If you're checking it yourself, avoid opening the cap directly when the engine is hot—cover it with a towel and unscrew slowly to prevent burns. For temporary top-ups, distilled water is recommended.

[OMax]

A sudden coolant temperature warning during a long drive is the scariest. Pay attention to two key moments when antifreeze disappears: check for water stains on the ground during cold starts, and look for spray marks in the pipes after the engine warms up. Rubber hoses under high temperature and pressure are prone to leakage at the clamp points. I once repaired a car where the leak was actually at the heater core joint. Many modern cars now use aluminum coolant pipes, and vibrations on bumpy roads can loosen the connections. For turbocharged cars, it's especially important to inspect the intercooler piping. If you notice low fluid levels, top it up to the marked line and monitor for a few days to gauge the consumption rate.

[SanIvan]

Our repair shop handles several cases like this every day. In addition to common leakage points, special attention should be paid to sand holes in the cylinder block or cylinder head. Recently, we found cracks in the water passage of a cylinder head during disassembly, causing coolant to be directly sucked into the combustion chamber. Turbocharged models also have a higher probability of leakage in the turbo cooling water pipes. In extreme cases, the radiator may freeze and crack in winter, with the damage only becoming apparent in spring. For self-maintenance, note the following: coolant should be replaced every two years, as prolonged use can corrode the radiator and cause leaks; when topping up, do not exceed the MAX line, as thermal expansion can cause overflow.