What are the symptoms of a broken radiator cap?

[StLukas]

A broken radiator cap may exhibit the following symptoms: 1. Coolant may spray out from the radiator cap. 2. After the coolant sprays out from the radiator cap, the flow rate and pressure of the coolant entering the engine will decrease. 3. Due to the reduced coolant flow, the engine heat cannot be dissipated by the coolant, leading to engine overheating or 'boiling over'. The radiator cap has three main functions: 1. Sealing. Under any operating conditions, the radiator cap should prevent coolant from leaking out. 2. When the coolant temperature rises and the pressure inside the radiator increases to a certain level, the radiator cap automatically opens the pressure relief valve, allowing excess coolant to flow into the auxiliary tank due to thermal expansion. 3. When the coolant temperature drops, the radiator forms a vacuum due to the coolant's contraction, and the radiator cap automatically opens the return valve, allowing the supplementary fluid from the auxiliary tank to flow back into the radiator.