NISSAN 21430-7999C Radiator Pressure Cap 88kPa

The genuine NISSAN 21430-7999C radiator cap (CAP ASSY-PRESSURE) is a precision pressure-regulating component essential for the safe and efficient operation of the vehicle cooling system. This genuine OEM part ensures that pressure in the cooling circuit consistently remains within the optimal operating range.

Operating Principle and Function

The radiator cap is not merely a simple closure element, but a dual-action valve (pressure relief and vacuum valve combined):

• Pressure Regulation (88 kPa): As coolant expands, pressure within the system increases. The cap's integrated spring-loaded valve opens precisely at 88 kPa (approx. 0.9 bar), allowing excess coolant to escape into the expansion tank (reservoir). This raises the boiling point of the coolant, preventing engine overheating.
• Vacuum Compensation: After the engine is shut off and cools down, the coolant volume contracts, creating a vacuum. The radiator cap's vacuum valve then opens, allowing fluid to return from the expansion tank, thereby preventing radiator hoses and the radiator core from collapsing or becoming damaged.

Technical Specifications

• Manufacturer: NISSAN (Genuine OEM part)
• OEM Part Number: 21430-7999C
• Alternative / OEM Reference Numbers: 214307995B, 21430-7995B
• Nominal Pressure Rating: 88 kPa (0.88 bar)
• Materials of Construction: Corrosion-resistant metal alloy housing, high-strength calibrated steel spring, and specialized EPDM rubber seals resistant to ethylene glycol and high temperatures.

Common Symptoms of Failure

Aging of the radiator cap or degradation of its seals can lead to serious engine issues. Inspection or replacement of the cap is recommended when observing the following symptoms:

• Persistent coolant leaks or white residue deposits around the radiator cap.
• Noticeable collapsing (flattening) of the radiator hoses after engine cool-down.
• Unexplained engine overheating even under normal operating load.
• Coolant boiling in the expansion tank at lower temperatures.