2004 Subaru Impreza Outback Sport, 200K
I went for a 50 mile highway drive at 60 - 70 mph. When I arrived, all the coolant that had been leaking from my car started to burn on the exhaust (visual confirmation) and I noticed the thermometer was near redline. I turned the car off and checked the oil (normal), timing belt (normal, not oily - i have a small cam leak), and coolant reservoir. The reservoir was totally topped up and probably the cause of the leak (no, I did not overfill).
Standing there wondering whether I should call AAA, the radiator suddenly started gulping coolant out of the reservoir and almost drained it. I refilled it with extra I keep in the car. I decided to drive it around a little at low speed, and then made it back home at ~50 mph the whole 60 miles back without any problems, overheating, or coolant overflow. It appears to be back to normal ... (knocking on wood).
The only other symptoms I notice are a that recently there is a bit of belt-like squealing on start up that tends to go away after some driving (hence the timing belt check). The noise is timed with the engine (louder/faster if I rev). I'm thinking it could be the water pump freezing up. The pump was replaced in 2014 along with the head gaskets. In 2016, the belt and sprockets were replaced when a bolt came loose in the timing compartment and wreaked some havoc (my bad), causing the belt to skip (almost destroying the engine!). Perhaps that incident damaged the pump, and I'm just now hearing about it?
Alternatively, 1) bubble in the coolant, 2) bad thermostat, 3) coolant really needs replacing at this point -- grime and stuff gumming things up, 4) head gaskets again! 5) radiator cap?
The car is totaled if I'm to take it to a mechanic, but I should be able to repair everything short of another head gasket leak.
Advice on where to start very much appreciated.