What Causes High-Temperature Coolant Spray in a Car?
4 Answers
It is possible that during the car's operation, the high-temperature environment of the engine causes the coolant to heat up, reach boiling point, and subsequently overflow. Alternatively, the coolant may not be circulating properly due to a thermostat not opening, a malfunctioning water pump, or a blockage in the water circulation system, leading to coolant spray. If coolant sprays out, it is recommended to pull over and let the engine idle for a while to allow the temperature to gradually decrease. Check if the cooling system is functioning properly and inspect the coolant level. Do not turn off the engine immediately, as shutting it down will stop both the cooling fan and coolant circulation, causing the engine to become even hotter. Open the hood to increase airflow and allow the water temperature to drop before removing the radiator cap. Turn it one notch and wait for the internal steam to escape before fully opening it. Do not add coolant immediately, as boiling water in a sealed container creates pressure. Opening the radiator cap right after boiling can cause the pressurized water to spray out, potentially causing burns. Afterward, check the radiator hoses for leaks. If the issue is caused by insufficient coolant, replenish it once the engine temperature has lowered. If coolant is unavailable, you may add a small amount of water as a last resort and proceed to the nearest repair shop for maintenance or replacement.
Last time I was driving on the highway, the hood suddenly emitted white smoke, which gave me a scare, and the coolant sprayed out directly. The mechanic told me it was most likely due to excessive pressure in the cooling system causing the radiator to burst, possibly because the thermostat was stuck and the circulation was blocked, or the radiator cap seal failed and couldn’t release the pressure. Another common situation is the aging of the cylinder head gasket, allowing high-temperature gases to leak into the cooling passages. Later, I added original coolant and replaced the radiator cap. Now, before long trips in the summer, I always check the fluid level in advance. If I notice the fluid level dropping, I become alert to potential water pump leaks or radiator cracks.
I've repaired quite a few vehicles that experienced coolant spray due to overheating, and the core issue always comes down to uncontrolled pressure in the cooling system. A stuck pressure relief valve in the radiator cap will cause fluid ejection, while a faulty thermostat that prevents coolant circulation is equally dangerous. The most common issue is aged hose ruptures - rubber hoses on cars over five years old are particularly prone to cracking. Corroded water pump impellers causing insufficient circulation also lead to overheating, with the most severe cases involving cylinder head porosity allowing exhaust gases to mix with coolant. I recommend flushing the radiator every 50,000 km and checking hose flexibility during coolant changes.
Over the years of modifying cars, I've found that coolant spraying out is usually related to temperature control failure. A clogged radiator hinders heat dissipation, and a non-functioning fan is even more troublesome. Worn or slipping water pump impellers prevent liquid circulation, and a damaged expansion tank is also a culprit. Last time, my friend's car blew the head gasket after turbocharging, allowing high-temperature gas to rush directly into the cooling pipes, instantly spraying coolant all over the engine bay. The key is to regularly change the coolant, especially for modified cars with higher loads—frequent checks are essential.
