The earlier advice is spot-on. I am not sure about the temporary "fix" (disconnecting the hoses at the firewall and inserting a pipe with clamps to route coolant away from the core) since every time I have removed these hoses, they've had to be cut away. When you do replace the core, change both heater hoses and the heater water valve as well. The valve is, at thirteen years of age, close to failure anyway. See the FAQ for more information.