I have a 1998 Subaru Legacy Outback. My daughter was driving last night and it just died on her. She said it was boiling over. I checked it out tonight thinking it was the thermostat. I changed that and filled with coolant let idle for about 10 minutes, the fans came on, so I took it for a spin. No more than got out the driveway and the temp shot up, turned around and popped the hood and the coolant was backing up into the overflow tank. Could it be a bad water pump? Any help will be greatly appreciated, you guys are great.