I have a 1991 legay AWD .. I bought it in Milford Ct, drove it 70 miles home in heavy traffi.. 70mph for a good part of the way.. next day, the car starts to overheat.. I get it to a dealer.. new thermostat, and coolant, same problem.. it can drive all day , no high heat, and then out of nowhere, it spikes... It has not blown out of the radiator, but has blown into the overflow.. I posted it for sale, but maybe, after reading some great posts, I should look into what you all here may think..any help would be great. thanks, Gug

I'd burp the cooling system. there is a little burp screw that needs to be opened on the top passenger side of the radiator. If you don't do this, you can get very weird issues. I'd start there, and see what happens.

I am having the same problem on my 97 Legacy 2.5GT. After owning it for a year and having no problems, I melter away the plastic tank of my radiator when it overheated 300 miles into a 500 mile trip.

 

Replaced radiator with a copper/brass from performance radiator (don't recommend). But the mechanic didn't change the thermostat. When I picked it up, i started it up and after 10 minutes idling opened the radiator cap to have some antifreeze spill out.

 

On the drive back, it started overheating after a 10 minute idling stop at a gas station. Did it again when I stopped to go to the bathroom and shut it off. When i drive, it's fine, and the fans work.

 

So I hope it's either the thermostat or I need to bleed it? But i remember opening up the radiator cap before and never bleeding it and it was fine up to now.

Both display symptoms consistent with a small internal headgasket leak.