What is the reason for water bubbling in the auxiliary water tank after the car stalls?

[Ora]

The reason for water bubbling in the auxiliary water tank after the car stalls is: After stalling, the water pump stops working, the coolant stops circulating, and the pressure in the radiator becomes lower than that in the auxiliary water tank, causing water to be drawn back into the radiator. The car radiator is a key part of the cooling system, maintaining the engine's heat through the circulation of antifreeze in the engine's water passages. The functions of the auxiliary water tank are: 1. When the engine temperature is high, part of the antifreeze can flow into the auxiliary water tank through the radiator cap; 2. When the temperature drops, the antifreeze in the auxiliary water tank can be drawn back into the cooling system through the radiator cap for cooling; 3. The auxiliary water tank has corresponding markings to indicate whether the radiator has sufficient water.

[LaLeah]

My car had this issue before too—it was quite scary when the coolant overflowed from the auxiliary reservoir after shutting off the engine. I thought about it for a long time, and it’s most likely because the engine overheated. After shutting off, the heat continued to build up, causing the coolant to boil. Common causes include a faulty radiator cap, which fails to maintain pressure and leads to coolant leakage, or insufficient coolant, disrupting circulation and raising the temperature even higher. Another possibility is a malfunctioning water pump or cooling fan—when the engine shuts off, the cooling stops, and the coolant expands and sprays out. The worst-case scenario is an internal engine problem, such as a blown head gasket allowing hot gases to enter the cooling system. If this happens, stop the car immediately and wait for it to cool down completely before checking the coolant level and radiator cap. Avoid touching hot components to prevent burns. Regular maintenance, including coolant replacement and system checks, is essential to prevent minor issues from turning into major ones.

[OKate]

A brief analysis of the reason why water spurts out after the engine stalls mainly points to an imbalance in the cooling system pressure. When the engine stalls after running at high temperatures, residual heat remains, causing the coolant to over-expand and spurt out. Common factors include a poorly sealed radiator cap leading to pressure leaks, insufficient coolant causing circulation failure, or clogged hoses causing backflow. The inspection method is straightforward: after the engine cools, check the coolant level and top it up, then try replacing the radiator cap with a new one. If the issue persists, it might indicate engine overheating due to a faulty water pump or internal leaks affecting overall temperature. Always monitor the temperature gauge while driving and address issues before the warning light comes on. It's best to have a mechanic inspect the fan and hoses during regular maintenance to ensure the cooling system remains unobstructed. Safety-wise, don't take this lightly, as the risk of burns is significant.

[AubreyAnn]

Water bubbling in the overflow tank after engine shutdown is a dangerous sign, indicating possible engine overheating and coolant boiling over. The causes usually include a failed radiator cap releasing pressure or insufficient coolant leading to system loss of control. Residual heat after parking causes water expansion and spouting. Failure to address this promptly can easily damage the engine, such as causing cylinder bursts. Immediately check the coolant level and cap integrity, avoiding operations during high temperatures to prevent burns. If the problem recurs, repairs are needed for possible hose blockages or internal leakage points.