Why do voltage regulators and ECUs melt. They been in the car for 40 years and all of a sudden decide they should melt (ooze really). Does this indicate a fault? Does everything eventually melt out and and fry something?

No, it's not a definite/scheduled thing. When electronic components go off-spec or begin to fail, they can heat up hot enough to melt the encapsulant and cause it to liquefy and run out of the box. Check the applicable system for excessive current draw and other faults, replace the dead "box" with a good one (getting harder to find good quality new "boxes" these days, but not yet impossible), and off you go.

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