Coolant Recovery issues

[68gmsee]

From this site: http://www.carcraft.com/techarticles...e/viewall.html

........Look for two rubber sealing gaskets on the nonvented cap. The normal seal on the very bottom is what seals the radiator pressure and is relieved only when the pressure exceeds the rating on the cap. The second seal will be located directly underneath the cap and is designed to seal the cap for use with overflow systems. The vented cap probably does not have this second seal under the cap and allows overflow out the tube where it is dumped on the ground.

[camrycurt]

Originally Posted by 68gmsee

........Look for two rubber sealing gaskets on the nonvented cap. The normal seal on the very bottom is what seals the radiator pressure and is relieved only when the pressure exceeds the rating on the cap. The second seal will be located directly underneath the cap and is designed to seal the cap for use with overflow systems. The vented cap probably does not have this second seal under the cap and allows overflow out the tube where it is dumped on the ground.

This is real interesting as I want to add a coolant recovery tank to my truck but was confused about what kind of radiator cap I needed to make it work. I'm planning on just running the overflow hose that now dumps on the ground into the overflow tank.

I don't understand the difference between the vented and nonvented caps. Isn't the concept the same with both caps, just with the coolant recovery tank you're allowing the system to suck up coolant instead of air once the system cools down? Why are there two different types of caps? In both scenarios you need a cap that vents coolant when it gets hot and expands and then draws back in once it cools, so shouldn't the same cap work for venting to the ground and into an overflow tank?

I don't mean to be dense, just trying to understand how the process works.

[68gmsee]

Upper seal keeps coolant in the system from escaping out of the top and basically keeps it an enclosed system.

Bottom seal opens up when radiator pressure exceeds cap pressure rating. Heat expanded coolant is then vented into reservoir.

When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the overflow tank to replace the water that was expelled. That would be the brass "check valve" in the bottom center of the cap.

From this site:http://ls1tech.com/forums/conversion...uestion-2.html

[camrycurt]

Originally Posted by 68gmsee

Upper seal keeps coolant in the system from escaping out of the top and basically keeps it an enclosed system.

Bottom seal opens up when radiator pressure exceeds cap pressure rating. Heat expanded coolant is then vented into reservoir.

When the radiator cools back down, a vacuum is created in the cooling system that pulls open another spring loaded valve, sucking water back in from the bottom of the overflow tank to replace the water that was expelled. That would be the brass "check valve" in the bottom center of the cap.

I see. So it's the addition of the brass check valve (and not the extra rubber seal) that differentiates the caps. That makes sense.

Thanks for clearing that up for me!