Well, it finally happened to me :(

The temp dropped to -15 F all night.  When I started the engine of my 85
Westy, Both heads were leaking antifreeze.  Power is now poor, engine sounds
different, & exhaust is not normal.

I tried some sealant for now, but I doubt it'll help other symptoms.

This engine was very well maintained, at least in the last 40,000 miles.
 From the looks of the rest of the van, the PO was also meticulous.  I find
it odd that both sides failed at the same time.

John Fleming