FrustratedWit

Please read to the end. We’ve done a lot so far and I’m looking for NEW ideas. Okay. So I’ve got a 2001 Outback that is giving my mechanic and I a run for our money. So far we have replaced: - Both head gaskets - Thermostat (twice!) - water pump & timing belt - radiator Here’s what happens: Driving in the city, heat on - no temp change Driving on the highway, heat on - overheats when idling, not while driving If I turn the temp to cold, the gauge goes back to normal, instantly. Today my mechanic bypassed the heater core because we suspected it was clogged. The car still overheated, after being driven at highway speed for 30 minutes, I turned it off, the coolant was at a normal level, the upper rad hose was Boiling and the lower one was warm, but firm. It took less than ten minutes to get back down to normal temp, and did not overheat the whole drive back. When I got home the coolant was at the same level but the upper hose and lower hose were the same temp. anything you can think of that hasn’t been tried yet?