Definition

Noun: - A removable, typically pressure-sealing lid or cover that fits onto the filling neck of a vehicle's radiator, designed to maintain the correct pressure within the cooling system and allow for the addition of coolant.

Usage

• The radiator cap is a critical component for maintaining the proper pressure in the engine's cooling system.
• Always ensure the engine is cool before attempting to remove the radiator cap to avoid injury from hot steam or coolant.
• A faulty radiator cap can cause the engine to overheat or lead to coolant loss.

Examples

Advanced Usage

• Pressure relief valve: A standard radiator cap contains a spring-loaded pressure relief valve. This valve opens at a specific pressure to prevent system damage and closes to maintain pressure when the coolant cools and contracts.
• Vacuum relief valve: Many radiator caps also include a vacuum relief valve to prevent the radiator hoses from collapsing when the coolant cools down and creates a vacuum inside the system.

Variants and Related Words

• Pressure cap: Another common term for a radiator cap, emphasizing its pressure-regulating function.
• Coolant reservoir cap: A cap for the separate overflow or expansion tank, which is a different but related part of the cooling system. (Note: This is a related but distinct component from the main radiator cap).

Synonyms

• Radiator pressure cap
• Cooling system cap

Related Phrases/Idioms

(This specific mechanical part is not commonly used in idiomatic expressions.)

Noun

1. cap on the opening in the top of a radiator through which a coolant liquid can be added