At 06:24 PM 8/25/2013, Jim Felder wrote:
>But here's my real question: would it be possible to buy some kind of
>one-way valve that kept pressure inside the system but sucked coolant from
>the "overflow" tank during cooldown, as the blue cap is designed to do, but
>just spliced into the hose between the cap and the overflow tank?

You'd have to have two valves in parallel but facing in opposite
directions, just like the cap does (whether or not they're in two
housings, there are two functions: easy suction toward the pressure
tank, and overpressure venting at 13 psi toward the overflow tank.

Probably the easiest way to achieve that is a radiator cap of the
type that's meant to suck coolant back from an overflow
bottle.  Fabricating an adapter to mate a cap to should be possible
but a nuisance given access to a dead radiator of the desired
type.  You'd have to cut the cap fitting off and braze across the
bottom of it a sheet incorporating a fitting for the hose from the
pressure bottle.  The fitting for the hose to the overflow bottle
will be already present.

Yours,
David