[chuzz]

There may be some air trapped in the cooling system. Park it on an incline (facing uphill) and remove the radiatior cap and run it until it gets warm and then top off the coolant. See if that works. Nice to see you have your ride going, but it stinks that the a/c doesn't work right now.

 

[VillageIdiot]

I went and got a thermostat yesterday. All that was available on a Sunday afternoon in this town for my particular engine was a 180F Motorad. The parts counter workers couldn't even find a [censored] thermostat gasket (their computer showed they had 10 in stock!) so I had to cobble one together with Permatex RTV, which so far seems to be holding without leaking. I tested the new thermostat in boiling water before I installed it. Dropped straight into a pot of boiling water, the new one was fully open in less than 15 seconds, the old one wouldn't even open in the slightest in that amount of time. The engine runs much cooler now, below the midpoint of the temperature gauge while driving. I just hope no permanent damage was done to the head or headgasket while the engine was running hot with the old thermostat

 

[chuzz]

Glad to hear you got it straightend out. Just keep an eye on your oil dipstick for water drops and watch the exhaust for white smoke for a while.

 

[B10alia]

That's decently normal for these cars in traffic. You don't really need to worry about much until the needle gets out of that range and moves toward that actual H mark. If it's not constantly running hot when it shouldn't be (city traffic is rough on the cooling system, lots of hot air and no movement through the radiator translates to higher temperatures for basically all vehicles) you shouldn't be too concerned. You'll know pretty quick off the head gasket starts to go.