What Causes Coolant to Boil While the Temperature Gauge Shows Normal?
3 Answers
Here are the reasons why coolant may boil while the temperature gauge shows normal: 1. The generator is not generating electricity, leading to poor heat dissipation. 2. Insufficient coolant level, which can easily cause the coolant to boil. 3. Geographical factors, such as being on a plateau, where overheating is more likely. Below are precautions for using coolant: 1. Try to use the same brand of coolant. Different brands use different metal corrosion inhibitors, so mixing them is not advisable. 2. Most coolants have a shelf life of two years. Ensure the product is within its validity period when adding. When replacing, drain the old coolant completely, clean the cooling system thoroughly, and then add new coolant. 3. Avoid diluting with water. Traditional inorganic coolants should not be mixed with water, as this can cause sedimentation and severely impair the coolant's function. Organic coolants can be diluted with water, but excessive dilution should be avoided. 4. For vehicles using coolant, never top up directly with tap water; use distilled or deionized water instead.
That day I was driving out for a countryside trip. Right after I parked, I heard gurgling sounds from under the hood - the coolant was bubbling and boiling, yet the dashboard temperature gauge still showed the middle position. After consulting a mechanic friend, I learned this situation was most likely caused by a faulty radiator cap seal. A normal cooling system requires sufficient pressure to raise the coolant's boiling point - a worn-out leaking cap can cause the boiling point to drop below 100°C. Another possibility is degraded coolant that's lost effectiveness from prolonged use - insufficient concentration can also cause premature boiling. After replacing both the radiator cap and coolant, the problem was solved. I'd suggest not opening the hood immediately after stopping - wait for the temperature to drop before checking if the coolant has deteriorated.
I remember last year my car had the same issue - coolant gushing out when climbing hills while the temperature gauge remained completely still. Later diagnostics revealed a faulty coolant temperature sensor stuck at a fixed position, perpetually displaying normal readings. Another possibility is a thermostat stuck in the closed position, causing localized overheating. Although the main circuit temperature appears normal, coolant around the cylinders can boil directly. If the water pump impeller is damaged or the radiator is clogged, coolant flow becomes restricted and vaporizes instantly at stagnant spots. Now I inspect the cooling system monthly, especially those rubber hoses - they must be replaced promptly when aged.
