[chrisp]

Stay away from GM orange Dexcool it is very troublesome. It is reactive with many types of gasket materials, also becomes very aggressive in attacking metals when air gets into the system. GM had and has a lot of trouble with this stuff, it does not tolerate any lack of owner maintenance and will make one hell of a mess if any leakage or a failure of the recovery system lets air into the cooling system. From simplicity and reliability old fashion green coolant is very good.

For the most part pressure kills aluminum radiators especially those with 1 inch and larger width tubes, when getting into cap pressures above 12 psi many of these radiators will balloon their tubes.

Keep tap water out of the cooling system, it comes with too many metal salts, chlorine, and sometimes fluorine; these things will etch the metal parts, especially any aluminum, and can act as an electrolyte making the coolant conductive as well as chemically active. Use either deionized or distilled water to dilute the coolant.

Zinc, on an activity scale, is not sufficiently far enough from aluminum to be very useful. Works better with copper, brass, and iron but it offers little if any protection for aluminum. Grounding of the radiator and heater is useful, these are in more modern designs mounted in rubber or plastic, so if the coolant is the least bit conductive these electrically floating parts will etch out. A big help is to ensure the engine is well grounded, especially the heads and intake should have independent grounds rather than hope the head bolts which are often installed with sealer are making a grounding connection with the block such that the transient spark voltages are grounded out through structure rather than coolant.