My girlfriend and I picked up a clean LL Bean Outback Wagon EZ30 H6 with 202,000 miles for a mere $1500 in Phoenix over the weekend. We paid the guy and no sooner than we get up the road and we found out the lower radiator hose had a leak in it. We replaced the hose and got it back to my parents house. The temp got into the red area on the gauge which is how we found out the hose was bad, but after that it was hovering on that line right before until I got going faster than 40 MPH, where it went back down to half. On Sunday, my dad and I tore it down and replaced the thermostat with a new failsafe unit, which was bad, replaced the coolant in the radiator, took it on a 15 mile test drive. On the test drive, it was fine until we got into traffic on the surface streets where the gauge would get up to the 3/4 line. On acceleration, the gauge would slowly creep higher until we got to speed and went back to half.
At first I immediately thought head gasket failure, but there is no loss of compression, the car doesn't smoke, the car doesn't misfire, I removed the cap from the coolant reservoir and there was no bubbling at all, in fact the level didn't even move about the Hot line on the bottle, there is no water in the oil, no condensation on the oil cap, none of the signs that the head gasket is blown. Not to mention, I've only found maybe a handful of instances where the head gasket on the H6 3.0 has failed and caused issues. We removed the radiator and flushed it out, the coolant looked like new, no crud inside in the radiator. When we remove the radiator cap and start the engine, the coolant splashes up like a geyser initially, but after that there is no movement of coolant inside the radiator. Is it possible the water pump has gone bad or there is a blockage inside the block, or is it a head gasket issue and I am one of the 1% who has experienced it?