Radiator caps and thermostats are essential components of a vehicle's cooling system. The radiator cap serves as a pressure valve that regulates the cooling system's pressure and prevents coolant from escaping. The thermostat, on the other hand, regulates the engine's temperature by controlling the flow of coolant into and out of the engine. If these components fail, the engine could overheat or fail to warm up properly. Regular maintenance of these parts is crucial to ensure optimal engine performance and prevent costly repairs.