Looking for help on what Caps should be used on Cooling System Supply and Overflow Tanks. My overflow has a Stant 13 psi and looks like supply tank is same psi with a release lever. Is this correct? Thanks .... 72 Pre-L 

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Sorry to ask another question related to tanks. should the overflow tank be empty or full like diagram? Mine is pretty much empty and supply tank is full.


With all of the air out of the system, and with the supply tank full, the recovery tank should be about half full.  This should be checked with the engine / coolant cold.


Thanks John, I believe I have any air purged out of system. I jacked rear end up a bit and opened front rad relief valve. Thanks for your recommendations. Ron

the overflow tank is to hold and to replace the coolant due to thermal swelling.

so when cold, the overflow should have a little in it, but when hot the level will increase.   then as the system cools down it will suck from the overflow.   If the overflow was too low when cold it could then suck air back into the loop.

(drawing is showing near full when HOT)

also, that illustration is the factory recomended arrangement.   I think the vent from the pressure tank to the radiator was a Service Bulliten.   In my opinion not a vary good way, because in air that makes it to the pressure tank will be vented to the top of the radiator.  I guess the thought is there it can be vented with that upper petcock.

and another opinion, air bubbles tend to go upward, so to get air out of the loop by venting at the top radiator, the front of the car needs to be raised


Thanks for the detailed information. I did vent from the top valve of radiator and got a bit of air/spitting when opened. I did drain some of the antifreeze (not much) and replaced with distilled water. Thanks again

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