Why Does Antifreeze Boil?
3 Answers
Antifreeze boiling, commonly referred to as "overheating," occurs when the high temperature of the engine during driving causes the antifreeze to heat up and reach its boiling point, resulting in overflow. When the boiling antifreeze comes into contact with hot metal parts, white smoke is produced. The reasons for antifreeze boiling include the following: 1. The radiator stops functioning, leading to excessively high water temperature. 2. Antifreeze circulation is blocked due to a malfunctioning thermostat (not opening), a non-operational water pump, or clogged water circulation pipes. 3. Insufficient antifreeze or poor-quality antifreeze with a low boiling point, making it prone to boiling. Solutions are as follows: 1. If antifreeze boils, it is recommended to pull over and let the engine idle for some time to allow the temperature to gradually decrease. Check whether the cooling system is functioning properly and inspect the antifreeze level. 2. If the boiling is caused by insufficient antifreeze, replenish it once the engine temperature has cooled down. In emergencies, a small amount of water can be added temporarily before heading to the nearest repair shop for maintenance or replacement.
I've been driving a taxi for over a decade and often encounter coolant boiling issues. Simply put, it means the cooling system can't handle the high temperatures. The most common cause is a poorly sealed radiator cap leading to insufficient pressure—normally at 1.1 bar, the boiling point reaches 120°C, but if pressure leaks, it drops back to boiling at 100°C. A stuck cooling fan or blown fuse is another reason. Once, my car got stuck on the cross-sea bridge with the fan not working, and the coolant bubbled up, nearly overflowing. A thermostat stuck in the closed position is even more dangerous—a colleague's car once needed an engine overhaul due to cylinder scoring from this issue. If this happens, don't push it: turn off the AC, switch on the heater, pull over, and shut off the engine. Remember not to touch the radiator cap within half an hour—last year, a repair shop apprentice opened it and got scalded by spurting boiling liquid, leaving his face covered in blisters.
Just got my driver's license and already encountered boiling coolant – it was terrifying. Last week, while driving my newly bought used car, white smoke suddenly billowed from under the hood. When I checked, the reservoir was bubbling like a hot pot. The mechanic said the coolant concentration was too diluted: a 50% antifreeze mix boils at 130°C, but my car only had a 30% concentration, causing it to overheat while climbing hills in hot weather. Corroded water pump impellers can also disrupt circulation – if debris jams the impeller, the radiator's top becomes scorching hot while the bottom stays cold. Cars with poorly modified intercoolers need extra caution, as greasy buildup on the cooling fins acts like a blanket. The mechanic taught me to check the water pump belt: when cold, pressing it should leave 12mm of elastic slack; too tight and it accelerates bearing wear. Now, I always glance at the coolant level before every trip.
