Originally Posted by mab864

Here's the set-up on pressure tank on my '13. The first cap on the radiator is just a sealing cap with no pressure relief spring. I presume the coolant in the radiator heats up and expansion moves it under pressure into the pressurized tank where it cools and then returns to the system. Here's a pic of the cap off the radiator.



And a close-up of the cap showing it's just a sealing cap with no relief spring.



The third pic shows the cap that is on the coolant tank which is a normal radiator cap. I think the idea of the system must be to increase the circulating capacity of the cooling system by 2-3 quarts. It's obviously not just an overflow system. I think this is the same type system on GT-R and the technology may have trickled down from that system.