99 legacy outback overheating - help!?

My engine overheated this morning on the way to work, ironically in subzero weather (99 outback wagon, 120,000 miles). About 10 minutes after I started it, within 2 miles of driving the temp guage climbed all the way to the top. I pulled over and idled, and it dropped back to normal (mid-guage), within 15 seconds, while the engine was running. However, about 10 miles later it started to creep up again, and I had to nurse the car for about 5 miles, coasting as much as possible, even shutting it off for a minute here and there to keep it from overheating. I brought it to a garage around the corner from work, and they said it needed a new thermostat and a coolant flush (seems reasonable. They said one of the radiator hoses was hot, but the other cold, thermostat wasn’t opening…) While replacing it, they say the looked in the water pump and that the fins are fine, it spins “a little too easily” but seemed to be tied into the drive belts. They put a new thermostat in, but that didn’t work, so they guessed it was a dud and tried another. At that point it worked while in the garage (both hoses became hot, engine temp stayed normal), but when they took it out for a test drive, it started acting up again. When he brought it back, he rechecked and one hose was now cold again. The mechanic is at a loss (not my usual guy, but I’m stuck 20 miles from home). Any thoughts? Help!


Was this car thawed out in the shop for an extended period? Was the coolant at the right concentration? This seems like a good possibility that the coolant has actually frozen and is not circulating.

Have they checked to see if there is a blown headgasket causing this?