I have just bought a used 96 Disco with a 4.1 in it. Heater core is shot, so I bypassed that. Having an overheating problem still though. I replaced the thermostat, flushed the system and ran straight h20 with no antifreeze and still have an overheating problem. I watch the guage go to almost 90%, then you see the thermostat open cause the guage drops drasticly to normal, then it blows all the coolant out of the cap. The engine heats up pretty fast in the morning at start up. Im afraid its something severe like a cracked block or head. Any ideas ?