I have a1997 Z71 5.7L w/ approx 150K miles. Leaking Radiator was replaced a little over 1 yr ago, then replaced again under shop warranty at 10 months after install. So far, no more problems with the radiator, but approx 3 months ago, the heater core was leaking and had to be replaced. A month later the new heater core was leaking again and was replaced. 2 wks ago, we again we found antifreeze had soaked the passenger side carpet, due to leaking heater core. We are now on the 3rd replacement heater core! It seems very unlikely to me that I have installed 3 bad heater cores in a row. Does anyone know what could be causing this problem? Someone mentioned to me there may be some blockages in some engine cooling ports, causing pressure build-up in the system, which is putting too much pressure on the heater core and causing it to leak. I really didn't think this was possible. Any thoughts / ideas out there?

 

What antifreeze are you running? Red or green? The red is acidic and the cores could have weak spots in the ones you installed. Flush your system real good. Use green antifreeze and another heater core.