Sorry to hear about your cooling problems. I had an issue with my cooling system for a year. I replaced everything and it would still leak coolant after it built up pressure. I never found out the source of the issue, but I did discover that my radiator prematurely failed 3 times. I have since replaced it with a zionsville superduty cooling kit (aluminum radiator, resorvoir and electric fan). I did that last February and I haven't had a cooling issue since. I have no idea why my cooling system was overpressurizing, but it was. I even had an indy shop do a compression check on the engine, pressure test the cooling system, analyze my coolant and oil. Everything was fine.
Hope this helps.