Grimmspeed 1.3 Bar High Pressure Radiator Cap

Managing engine temperatures can be tricky, but one thing is certain: increasing the pressure in your cooling system directly improves its efficiency. The factory 1.1-bar (16 PSI) radiator cap works fine for normal driving with a standard antifreeze mix, but enthusiasts who push their Subaru harder—or run water or antifreeze/water blends for better heat transfer—often run into overheating or expansion tank overflow due to the lower boiling point of these fluids.

A higher-pressure radiator cap is the simplest and most cost-effective way to raise the boiling point, stabilize temperatures, and keep coolant where it belongs. The GrimmSpeed 1.3 Bar High Pressure Radiator Cap offers an immediate improvement in cooling system performance along with a clean, upgraded look under the hood.

Quick Specs

• 1.3 Bar / 18.9 PSI Rating – Raises the boiling point for improved cooling efficiency
• Electro-Coated Stamped Steel – Durable, corrosion-resistant construction
• Heavy-Duty Silicone Seal – Ensures consistent pressure and leak-free operation
• Clean, Low-Profile Design – Replaces the OEM yellow cap with an understated, performance-focused look
• Manufactured in Japan – Built to high standards for long-term reliability

Fitments:

• All Subaru Radiators and/or Expansion Tanks
• Many (but not all) Nissan, Mitsubishi, Honda, Mazda, and Toyota Models

Fitment Note: Not suited to replace the 1-way "earless" cap on the STI radiators, but will work perfectly on the upper expansion tank!