I've also experienced the radiator boiling over while delivering goods in a van, and it felt quite scary. It's usually caused by a failure in some part of the cooling system, such as insufficient water pump pressure or worn-out blades, where the water flow becomes as slow as a turtle, causing heat buildup and boiling. As for the fan, it might have poor contact or a faulty motor, failing to keep up with heat dissipation. The thermostat often gets stuck in the closed position, blocking the passage. Worse yet, a leaking cylinder head gasket allows engine gases to mix with the coolant, causing sudden pressure changes and boiling. Improper coolant concentration or insufficient levels can also easily cause problems, especially in scorching summer heat. I suspect your van might have been running under heavy load for too long, overwhelming the fan. Once, it happened to me on the highway—the rearview mirror was filled with white steam, and I was so scared that I immediately turned on the hazard lights and pulled over, pouring water to cool it down, almost risking engine damage. Afterward, I went to a mechanic, who replaced the thermostat and flushed the radiator to fix it. For regular maintenance, I remind myself to keep an eye on the temperature gauge—if it spikes, don’t push it; getting home safely is the priority. Before every trip, I quickly check the coolant reservoir—it’s cheap and saves a lot of trouble.
