On a '72 Supreme coolant reservoir, how does the coolant return to the radiator if there is no bottom return hose? And if it doesn't return to the radiator, then why is there an "add" and "full" level on the reservoir?

Things that make you go "hmmm"🤔🤔🤔

 

The cap opens or releases when the pressure gets too high and coolant goes into overflow tank. On cars before the overflow it just went out tube and was lost. Then after car is shut off and coolant pressure drops radiator cap lets coolant come back thru tube into radiator. Thats why you need a cap that is made for a overflow tank- most are. When you remove the overflow cap, there is another tube that goes down into the tank isn't there? Should be.

 

The same way the windshield washer tank can feed washer fluid from the cap. There's a tube that runs from the cap down into the tank.

 

Well, now looking at your other thread I see you changed tanks. Is the second one supposed to be a original style? I can't tell if you have a tube inside the cap that goes down to about 1/2 " from the bottom of tank so it can siphon coolant back into radiator. If you don't have that no it won't work take coolant back into the radiator.

 

It is the original style, and there is no tube going into the reservoir from the cap. I'll check tomorrow to see if I missed that on installation.

 

The cap has got two barbs. One just goes through the cap and stops at the inside plane of the cap, the other has a barb on the inside. That one, with the channel with barbs on both sides, takes the hose to the radiator, and the 4 inch or so long hose to the bottom inside the jug. The other barb on the outside is the overflow hose, idea being is that jug will fill to MAX FULL in a "thermal event" and will start coming out the overflow (my money is it will blow the cap off).