I just changed the leaking heater core on my parents 1995 Caprice and found
directions requiring a 50/50 mixture of distilled water (not tap water) and
all vehicle anti-freeze (meaning for aluminum parts).  The heater core was
just changed two years ago for the same problem.  The directions also called
for check of less than 0.1v from water in system and ground to avoid
electrolysis and another hole in radiator or heater.   The directions also
wanted check for ph factor.

The heater core seems to be suspended by rubber hoses; does not touch where
it goes through the firewall; and is screwed under dash to plastic ducts.
This should not be a problem with electrolysis similar to a union used in
plumbing.

I had Mister Goodwrench fix my intermittent ground problem over four years
ago when he also found a leaky water pump and wanted to replace the
distributor for an estimated $1200 total.   I let Chevy fix the ground
problem.  I replaced the water pump and the car ran without ignition problem
till last spring.  When the ignition hiccupped, I replaced plug wires and
distributor.   Changing the plug wires was 20 times more involved than on
all my old cars without computer!!!  Last summer when the A/C wasn't working
and glove box switch for trunk lid would not open Chevy again found a bad
ground.

It could be that my electrical system is killing these heater cores.

Any thoughts?

Gary