What Causes Coolant to Boil and Overflow?

[VonEvan]

Coolant boiling and overflowing is caused by a damaged radiator or a connection between the oil seat and the water channel. Below are specific details about coolant: 1. Definition: Coolant, whose full name should be antifreeze coolant, refers to a cooling liquid with antifreeze properties. Antifreeze prevents the coolant from freezing and expanding in cold weather, which could crack the radiator or damage the engine cylinder block. Antifreeze is not only for winter use but should be used year-round. In regular car maintenance, the engine coolant should be replaced every year. 2. Function: Coolant is an essential part of a car engine. It circulates within the engine cooling system, carrying away excess heat generated during engine operation to maintain the engine at its optimal working temperature. Insufficient coolant can lead to overheating of the engine, potentially causing damage to engine components. If a car owner notices low coolant levels, they should top it up promptly.

[PhoebeLee]

I've experienced coolant boiling while driving, which is usually caused by engine overheating. Common causes include the radiator fan not working or the thermostat getting stuck, preventing timely heat dissipation; coolant leakage leading to low levels that are prone to boiling; a pressure cap aging or sealing poorly, causing the boiling point to drop after losing pressure; a water pump failure preventing coolant circulation; or a damaged cylinder head gasket allowing combustion gases to enter the system, increasing pressure. Once I notice the temperature gauge spiking or see smoke while driving, I immediately slow down, pull over, turn off the engine, and let it cool for at least half an hour before opening the hood to inspect. Continuing to drive otherwise could cause internal engine components to melt or deform, resulting in exorbitant repair costs. It's important to develop the habit of checking coolant levels monthly and clearing debris in front of the radiator, as well as replacing the coolant annually to prevent clogging.

[SanSienna]

From personal car repair experience, the main cause of coolant boiling is issues in the cooling system. Insufficient fluid level is the most common problem—check if the reservoir is full. A malfunctioning radiator fan fails to blow air, preventing heat dissipation. A thermostat that doesn't open the main circulation or gets stuck closed, a broken water pump that stops circulating coolant, or a failed pressure cap that can't maintain pressure—these factors cause temperature to spike uncontrollably, leading to coolant expansion and boiling. For handling, I recommend turning off the engine and stopping the car first. Ensure the engine cools down before slowly opening the cap to add fluid or calling for repairs. For prevention, regularly flush the cooling system, use high-quality coolant, and test component functionality. The key is to frequently monitor the temperature gauge and address issues early to avoid costly and troublesome engine damage repairs.

[AlanaAnn]

When I first started driving, I also experienced coolant bubbling out, mainly caused by overheating. Possible reasons include poor heat dissipation, such as a fan stopping or a thermostat getting stuck; or coolant leakage leading to low fluid levels; or a faulty pressure cap failing to maintain pressure. If this happens, stop the car and turn off the engine immediately to avoid further driving that could lead to engine failure. Safety first—after turning off the engine, wait for it to cool down and check if the fluid level is sufficient. Regularly checking the coolant condition every three months can prevent problems, especially before long trips, ensuring a more worry-free drive.