What is the reason for the water kettle overflowing when the car temperature is not high?

[StCourtney]

There are two main scenarios for the water kettle overflowing when the car is not overheating. Below is a detailed explanation of the specific reasons for these two situations: 1. Overflowing from the radiator when the accelerator is heavily pressed: This is mainly because the wet cylinder liner or cylinder head has significant gaps or cracks. When the engine is running, the pressure of the compressed air or combustible gas in the cylinder is greater than the pressure of the coolant in the cooling channel, causing these combustible gases to enter the engine's cooling channel through the gaps, resulting in the water kettle overflowing. 2. No air in the coolant when the engine is running: Whether the water temperature is high or low, pressing the accelerator should direct coolant towards the radiator's filler neck rather than spraying it out, and releasing the accelerator should cause coolant to spray out from the filler neck.