Have a 00 TJ, 131k, 4.0l auto. Coolant has to be added every couple days, but no visible leaks. Last month - new rad, thermo, cap, n hoses. Still using (to somewhere) about cup of coolant every couple days or so of running. But no leaks. And, after adding, upon chking next day or so, "extra" is now in overflow tank! Tank is now overfull. Chged top hose to overflow n tightened to no avail. But never coolant back when it gets a bit low! I've heard it could be any/all of following: heater core (had luke warm heat last yr...back flushed, good heat now), freeze out plugs?, cracked head? Not necessarily in that order. Anyone else with same symptoms? Ideas? Thanks in advance!