What Causes a Car Radiator to Boil Over? How to Handle It?

[VonPeter]

There are several reasons and solutions for a car radiator boiling over: 1. Radiator malfunction: When repairing by welding, the damaged cooling core tubes are blocked, reducing the water flow area and decreasing the water output from the upper chamber. 2. Deformation of radiator cooling core tubes: The inner layer of the radiator inlet hose delaminates, reducing the hose's flow cross-section, obstructing water flow, increasing resistance, and decreasing water output from the upper chamber. 3. Excessive scale in the radiator: Core tubes are clogged with sludge, scale, or debris, hindering water circulation. The flow resistance in the upper chamber increases, reducing water volume. Cylinder gasket erosion, cylinder liner cracks, or high-pressure gas entering the water channel can also cause issues. 4. Overly soft water pump inlet hose: The vacuum suction from the water pump causes the hose to collapse; reversed fan blades, broken belts, or faulty water pump impellers prevent forced water circulation. Reduced cooling water circulation area and increased temperature decrease the hose's water capacity, causing the excess cooling water to be expelled from the radiator filler neck, resulting in water spraying.

[VonKiara]

When I was younger, I drove a truck, and the radiator boiling over was mostly due to insufficient coolant or a blocked system. Engine overheating causes the water to boil and spill out. Quickly turn off the engine and park the vehicle safely, then wait at least half an hour for the temperature to drop. Don’t recklessly open the cap—beware of burns or steam blasts. Check the coolant level; if it’s too low, add distilled water or specialized fluid. Also, see if the fan is running and check the belt tension. Preventive measures: Regularly flush the radiator, keep the coolant fresh, and monitor the temperature gauge in traffic. I remember one time I neglected it and stubbornly kept driving, resulting in a warped cylinder head and a repair bill of over a thousand bucks—a hard lesson learned.

[VonMalia]

When I first bought the car, I encountered the radiator boiling over, which was really scary. The possible causes could be water leakage, a broken water pump, or a fan failure. The response must be decisive: immediately turn on the hazard lights, pull over, and turn off the engine—don't push it further, safety comes first. After the car cools down, put on gloves to check the radiator cap's seal and hoses for any cracks. It's best to top up with spare coolant if available; otherwise, call a tow truck to take it to a repair shop. I now check the radiator and fan operation every three months to avoid issues before long high-speed trips. If the radiator boils over, don't panic—always consult the manual before taking action to prevent secondary engine damage.

[NevaehLynn]

I often drive the family car to pick up and drop off the kids, and an overheating radiator is really worrying. Simply put, this can happen if there's too little coolant or a blocked pipe, leading to engine overload and thermal runaway. Stopping to rest is crucial—wait at least twenty minutes for cooling. Check for water stains on the ground? If there's a leak, don't open the hood yet. Prevention requires regular maintenance: inspect the cooling system when seasons change, and top up with antifreeze mixed evenly. Money-saving tip: use genuine parts, don't cheap out and buy fakes. Staying calm is key—safely park the car before handling the issue.