I have a 2004 Jeep Wrangler unlimited. When I purchased it last year it had a bad heater core. I replaced the core and after a couple of days I was leaking fluid again. This time it was coming from the coolant lines that attach to the radiator. I tightened the hose claps and all was good for about 6 mounts. This time the top of the radiator was leaking. The P.O. had replaced this rad less than 5 years prior. I replaced the rad and again all was good for about 6 mounts. Now the heater core is leaking again. Any ideas about what keeps causing the failures in the coolant system? I use a premix universal antifreeze so no tap water or cross mixing types of antifreeze.