Koyorad Radiator Cap SK-C13 16 lb Pressure — OE-Grade Universal Fit, Corrosion-Resistant

The Koyorad Koyo SK-C13 Radiator Cap is a 16 lb, OE-grade replacement cap engineered to maintain proper cooling-system pressure and reliable seals for Koyorad radiators and universal applications.

Built from durable materials selected to match original-equipment standards, the SK-C13 cap is designed for long-term exposure to engine bay heat and road conditions. Koyorad uses aluminum, brass, copper and heat-resistant plastics in its components so the cap resists corrosion, spring fatigue and seal hardening that can lead to coolant loss or pressure failure. This is a simple, direct part intended to restore correct pressure control in compatible radiators.

How does the SK-C13 maintain the correct cooling-system pressure?

The SK-C13 holds a 16-pound (psi) pressure rating to keep coolant in the radiator until the system reaches the intended boiling point. A calibrated spring-loaded valve opens at the set pressure to let excess coolant flow to the overflow reservoir, then closes to reseal the system as it cools. The reliable spring and valve tolerances help reduce premature venting and coolant evaporation.

• 16 lb pressure rating suitable for higher-boiling coolant performance
• Spring-loaded relief valve calibrated for repeatable opening/closing
• Durable elastomer seal to prevent slow leaks and vapor loss

What materials and construction features extend the cap’s lifespan?

Koyorad selects OE-grade metals and plastics that withstand heat cycling and corrosive coolant environments. Key components — such as the valve, spring and sealing surfaces — are crafted from corrosion-resistant metal and high-temperature elastomers, minimizing wear and seal degradation over time. This construction reduces the need for frequent replacements in most driving conditions.

• Corrosion-resistant metal components (aluminum, brass, copper)
• Heat-stable plastic and elastomer seals resistant to hardening
• Precision assembly that maintains valve tolerances across cycles

Is the SK-C13 compatible with my radiator or vehicle?

The SK-C13 is specified as a universal-type 16 lb radiator cap intended for use with Koyorad radiators and many aftermarket or OE systems that accept this size and pressure rating. Confirm fitment by comparing cap diameter, seat style and pressure rating to your original part. When in doubt, check Koyorad compatibility charts or consult a service manual for seat dimensions and required pressure.

• Universal 16 lb cap fits many radiators using the same seat style
• Recommended for direct replacement on compatible Koyorad radiators
• Measure cap seat and verify 16 psi requirement before installation

How should I install and maintain the SK-C13 for best results?

Installation is straightforward: ensure the radiator neck and mating surfaces are clean, press the cap on and twist until it locks into place. Inspect the seal periodically for cracks or hardening and replace the cap if the spring feels loose or if coolant leaks occur. Proper coolant level and overflow tank condition also help the cap function correctly.

• Clean filler neck before mounting to ensure a tight seal
• Turn to lock; listen and feel for secure engagement
• Inspect seals and spring annually or during coolant service

Who this product is for: The Koyorad Koyo SK-C13 Radiator Cap is aimed at DIY mechanics, professional technicians and vehicle owners who need a durable, OE-grade 16 lb replacement for Koyorad or similarly configured radiators. It's a practical choice when restoring proper pressure control after maintenance, replacing a worn or leaking cap, or upgrading to a reliable, long-lasting component for everyday driving and performance applications.