What Causes Coolant to Spray Out?

[VanAlexander]

There are primarily two reasons for coolant spraying out: 1. Radiator damage. The automatic transmission fluid is cooled by the radiator. If the cooling tubes inside are damaged, the fluid will leak into the radiator. 2. It could be due to a breach between the oil chamber and the coolant passage. Since this vehicle's oil filter housing has coolant passages for cooling, corrosion or high oil pressure can cause oil to enter the coolant passage, though a blown head gasket is less likely. 3. Radiator damage, poor sealing of the upper and lower water chambers leading to coolant leakage; or loose connections and poor sealing at the overflow tank, water pump joint, and other cooling system pipe fittings causing coolant leakage.

[Quintero]

I've repaired many cars with coolant spraying out, mostly due to the cooling system failing. The most common issue is aging and cracked coolant hoses, especially rubber ones that have been used for seven or eight years—they can burst suddenly under high temperature and pressure. A stuck pressure valve in the radiator cap can also cause coolant to spray out from the overflow tube, like a pressure cooker releasing steam. Once, I encountered a driver who opened the radiator cap right after a high-speed drive, and the scalding coolant sprayed onto the hood, hissing and smoking. If you smell coolant's sweet odor along with white exhaust smoke, there's a high chance the head gasket is blown. In such cases, never force the engine to run—pull over immediately, shut it off, and call a tow truck, or the engine could be ruined. Regularly check the coolant level in the overflow tank, and if the coolant appears yellow and murky, replace the entire system.

[SanLyla]

Last year I had a nasty experience with coolant spraying. While driving, the dashboard suddenly lit up with a red warning light, followed by white smoke billowing from the hood gap. After pulling over, I found the overflow tank gushing blue liquid like a fountain, and touching it left a small blister on my finger due to the heat. The repair shop diagnosed it as a failed radiator seal ring, where pressure forced coolant out from the weak spot. The technician tested it with a pressure gauge—normal 1.1 bar pressure had spiked to 1.8 bar. Later I learned the thermostat was stuck, causing circulation issues. Now during every service, I make sure the mechanic checks the cooling system, and rubber hoses get replaced every four years without fail. Before summer road trips, I always squeeze the coolant hoses when the engine's cold—if they feel stiff, it's replacement time.

[LeJulia]

Coolant spray is mostly caused by a loss of pressure control in the cooling system. When the temperature exceeds 110°C, the volume of coolant expands by more than 5%. At this point, the pressure valve in the radiator cap should release the pressure, but if the valve is rusted and stuck, it can cause a rupture at the weakest point. Common spray locations include radiator seams and heater hose connections. Once, I saw a modified car with its overflow tank spraying like a whale spouting water—after a long inspection, it turned out the turbocharger caused insufficient radiator capacity. A reminder: after modifying the engine, you should increase the radiator capacity by at least 30%, as the stock cooling system can't handle it. If you hear gurgling sounds in the radiator after parking, be alert.