Coolant caps
Coolant caps seal the expansion tank or radiator and control internal system pressure. Small in size, but crucial for safe and stable engine cooling.
A coolant cap is more than just a cover — it's a pressure valve that manages the balance within a closed cooling system. As the engine heats up, coolant expands, increasing pressure. The cap maintains that pressure at a safe level, usually between 1.0 and 1.5 bar, by allowing steam or fluid to escape when necessary.
When the system cools down and pressure drops, the cap also allows air or coolant to return, preventing vacuum formation and maintaining consistent fluid levels. A worn or faulty cap can lead to coolant loss, air bubbles, or pressure imbalance — all of which negatively impact the cooling system's performance.
Coolant caps come in various pressure ratings and mounting styles (threaded or bayonet). They must withstand extreme heat, chemical exposure, and frequent pressure changes without failure.
Key features and uses:
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Maintains safe operating pressure within the cooling circuit
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Prevents overpressure, vacuum, and fluid loss
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Ensures stable expansion and return flow
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Available in multiple designs and pressure levels
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Critical for maintaining a sealed and reliable cooling system
At Sanders Parts, we offer high-quality coolant caps built for performance, durability, and a perfect fit — keeping your cooling system sealed and stable, no matter the conditions.