Coolant Bottle Cap (also called a radiator reservoir cap or coolant reservoir cap) is a small but essential part of the engine cooling system. It seals the coolant expansion bottle to maintain system pressure and prevent coolant leakage or contamination.
Key Functions
Seals the coolant reservoir: Prevents coolant from spilling or evaporating.
Maintains pressure: Keeps the cooling system pressurized for better heat transfer.
Controls flow: Some caps include a pressure relief valve to release excess pressure safely.
Prevents contamination: Blocks dust, dirt, and moisture from entering the coolant system.
Typical Features
Durable plastic or metal construction
Pressure-rated spring valve (in pressure caps)
Threaded or twist-lock design for secure fit
Rubber gasket or O-ring for leak-proof sealing
Benefits
Helps maintain correct engine operating temperature
Prevents coolant loss and overheating
Protects engine components from thermal stress
Low-cost yet critical for engine reliability