Toyota Radiator Cap Sub-Assembly 16401-31650 – Direct-Fit, Factory Pressure Rating

Toyota 16401-31650 Radiator Cap Sub-Assembly is the factory-style pressure cap that seals the cooling system and helps maintain proper coolant pressure.

This genuine-style radiator cap replaces the original and is built to match Toyota's specifications for fit and function. Designed for direct fitment, the sub-assembly provides a secure seal for the expansion tank or radiator neck, helping the cooling system operate as intended under normal driving conditions. It’s a compact replacement part that’s simple to install yet critical to overall cooling performance.

How does this radiator cap affect cooling system performance?

The cap controls the pressure threshold in the cooling circuit, which influences boiling point and coolant flow. A correct-pressure cap helps prevent premature boiling and minimizes the risk of coolant loss through overflow. Using the right cap keeps the system balanced and supports consistent engine temperatures.

• Factory-spec pressure rating matched to Toyota requirements
• Secure sealing gasket reduces coolant evaporation and leaks
• Robust spring mechanism maintains pressure under heat cycles

Is this part an exact replacement for the original Toyota component?

Yes — the sub-assembly is manufactured to align with the original part’s dimensions and performance characteristics. That means it installs without modification and works with the existing neck and overflow plumbing. Choosing a matching part number reduces fitment issues and simplifies service.

• Direct-fit design for straightforward, no-modification installation
• Compatibility with vehicles specified by Toyota for 16401-31650
• OEM-style materials for long-term durability

How do I install the radiator cap and what maintenance is needed?

Installation is quick: remove the old cap when the engine is cool, inspect the filler neck, then press and twist the new cap into place until it seats. Periodically check the cap and neck for corrosion, cracks, or degraded seals and replace if any damage appears. Always follow safety precautions and only open the system when the engine has cooled.

• Install only on a cold engine to avoid scalding from hot coolant
• Inspect gasket and spring for wear during routine coolant checks
• Replace if cap fails to hold pressure or shows visible damage

What materials and construction ensure this cap lasts?

The assembly combines corrosion-resistant metals and heat-tolerant elastomers engineered to withstand repeated thermal cycling. The spring and sealing surfaces are designed to retain their properties over many heat-and-cool cycles, helping the cap maintain consistent pressure control. Durable construction reduces the frequency of replacements compared with lower-grade aftermarket options.

• Metal body components resist rust and deformation
• High-temperature gasket materials maintain a reliable seal
• Quality spring hardware preserves set pressure over time

Who is this for: Ideal for Toyota owners, independent mechanics, and fleet maintenance teams that need a dependable, OEM-compatible radiator cap. If you require a direct-replacement component that fits precisely and restores the intended pressure control of the cooling system, this sub-assembly delivers a straightforward, durable solution.