About a year ago I posted some messages concerning a 92 Caprice that I had replaced the heater core in and it lasted only 30 days or so before leaking again. Got a replacement, same story, 30 days to the day and it sprung a leak as well.
Got number 3 and same story so this time I tossed in some stop leak and have lived with it over the summer, but now it is winter and while the stop leak fixes the holes as soon as they occur, I have to do something.
I went down the electrolysis path, defective unit, installation problems (meaning I was breaking them) and so forth and never got anywhere until...........
I had replaced the factory hoses which have those quick disconnect connectors, are bent like pretzels and consist of a metal and rubber mess, with normal heater hose because they cost over $100 for both of them and only GM makes them.
That was the mistake that killed me.
Turns out, the factory hoses have a check valve and a restricter in them which limits the flow, and back flow through the heater core.
Obviously my replacements did not, and if you look at the factory hoses you will not see these valves as the hose is encased in aluminum , plastic, rubber and that coiled protective sleave stuff they wrap wiring harnesses in.
The FSM is completely wrong as well because the pictures show an external valve, yet the description says the valve was eliminated for 1992. Even the parts guy at GM was confused!!
FWIW, I got the new hoses, a new heater core and all is well!!!
Hope this helps another poor soul who may think about the same thing.
psycho.