Radiator Cap by Mishimoto. 1.1 Bar. Getting the most out of your performance parts comes down to the details. When faced with hard driving conditions, a vehicle�s cooling system becomes highly pressurized. OEM caps are not equipped to handle higher pressure, causing fluid to leak out into the overflow reservoir. The Mishimoto radiator cap is rated at a higher pressure and will keep coolant where it needs to be-flowing within the system.