Thermostat for 460 Cobra

[cycleguy55]

Originally Posted by RockBit

I have a question about this. If the overflow tube is above the radiator cap, I can see how excess coolant will overcome the cap pressure and be vented to the catch can. I cannot see how coolant can be sucked back into the radiator from the catch can, because the (pressure) radiator cap is closed.

What am I missing?

Radiator caps have 2 functions.

1. hold pressure until the design pressure is reached
2. allow return of coolant when the engine cools, the pressure drops and a vacuum is created.

Check the 1:15 minute mark of this video: https://www.youtube.com/watch?v=QhLUwsCdM08

[RockBit]

Originally Posted by cycleguy55

Radiator caps have 2 functions.

1. hold pressure until the design pressure is reached
2. allow return of coolant when the engine cools, the pressure drops and a vacuum is created.

Check the 1:15 minute mark of this video: https://www.youtube.com/watch?v=QhLUwsCdM08

Thank you for the aha moment. I did not realize there are two types of radiator caps, vented and non-vented. The vented type has a second valve to allow coolant to be pulled back into the radiator from an overflow tank.

I get it.