NISSAN 21742-VC300 Coolant Reserve Tank Hose

Genuine Nissan OEM coolant reserve tank hose (part number: 21742-VC300). This premium quality component is a vital element of the vehicle's cooling system, connecting the radiator to the reserve tank (expansion tank) to ensure smooth, safe coolant flow during thermal expansion processes.

Function and Importance

During engine operation, the coolant temperature and volume fluctuate continuously. The purpose of the coolant reserve tank hose (HOSE-RESERVE) is to route expanding, excess coolant to the reserve tank, and then return it to the main cooling circuit via the resulting vacuum as the system cools down. This process prevents excessive pressure buildup, minimizes coolant loss, and stabilizes internal cooling system pressure.

Technical Features and Material Quality

Manufactured according to the stringent quality standards characteristic of genuine Nissan parts, this hose offers the following features:

• Material Composition: High-grade EPDM (ethylene propylene diene monomer) rubber with internal fiber reinforcement, providing outstanding resistance to high temperatures, cooling system chemical additives (glycol), and ozone.
• Pressure Resistance: Optimized wall thickness and structural design engineered to withstand operating cooling system pressures and sudden pressure fluctuations.
• Flexibility: Excellent vibration-absorbing capability, preventing stress and loosening at connection points during natural engine movement and vibration.
• Design: Precise factory pre-formed shape and routing for stress-free installation.

Typical Signs of Wear and Failure

Under continuous thermal stress and aging, rubber components lose their flexibility over time. The most common signs indicating failure include:

• Visually identifiable cracks, fissures, or surface degradation.
• Softening (sponginess) of the hose, or conversely, the rubber becoming hard and brittle.
• Coolant leaks or antifreeze residue around connection points (clamps).
• Hose wall collapse under vacuum, restricting fluid flow and impeding system bleeding.

Why Choose Genuine (OEM) Parts?

Genuine Nissan parts ensure a perfect fit and long service life. Unlike universal or substandard aftermarket hoses, the genuine hose accurately follows engine bay geometry, preventing kinking, chafing against adjacent components, and cooling system failures caused by premature material fatigue.