From the guy selling the beater Syncro:

<<The rear bench is out, as I had intended to replace the core, but for now
the valve is closed and the core is in a plastic bag to prevent it from leaking
onto the floor.>>

Once I think I have heard it all by way of this list, something perks up my
ears.  I applaud the creative problem solving, but there are more suitable
solutions for a leaky rear heater core.

For example:

1/ If the core is already in your hands, why not pinch off the lines and
expend the extra 5 minutes to replace it?

2/ Shunt the lines with a piece of metal tubing.

3/ Plug the lines with almost anything that will fit, even spent shotgun
shells.

4/ Do what any man who has ever had to stop a hose in an emergency has done,
"crimp" it by folding it over on itself.  Then seize the "crimp" with some
bailing wire.

But, ya doesn't have to Baggie it.  I have this image stuck in my head of an
ever swelling Hefty bag undulating like a pregnant hippopotamus in the back of
a van.

George