Dart cooling system

Lotta damage is electrolysis.

When we checked antifreeze, looking for "clean and green, good to -35* ", - we'd also check PH and often give the coolant a little ph + or - when nec.
Simple litmus paper test, or "ph" pen .
(Swimming pool chems)
When a car blows a head gasket, the coolant can get very acidic from the combustion contaminants, but still looks brand-new.

If left acidic, nasty things happen, and ph adjustment is strongly recommended.