After being parked outside for 3 days in subzero temps, the G is now overheating quickly, after about 6 miles on the road. First time this happened, it was on the drive home from the airport, after sitting outside.

Heater is on full blast, but only cold air is coming out; radiator has no leaks, oil temp gauge (aftermarket) doesn't show particularly high temps, about 180 or so, which is normal. Radiator is fully bled, no air bubbles (or no more so than normal), fans both work, etc...

Does this mean thermostat is stuck closed?

Or might it be something else?

I let the car sit in thee warm garage for a couple nights (business trip) after this happened, so if the thermostat froze, it should have unfroze by now.

any ideas?

No engine codes, other than P1217 which is the engine coolant temp overtemp code.

 

I had the same problem. Thermostat was the issue. Feel the hoses, and if they are cold after it starts overheating, then it is a pretty good indication the spring in the thermostat has frozen and doesn't have to do with temperature, as mine happened in the summer. The other option is the headgasket, but odds are it isn't. Thermostat is an easy fix at around $250.00

Good luck

 

"Heater is on full blast, but only cold air is coming out...."

Even with the thermostat stuck closed, the heater should be putting out warm (or hot) air. The thermostat only controls flow to the radiator. Coolant is always flowing to the heater core.

 

so then what could it be?

 

$250 to replace a THERMOSTAT???

 

 

Air bubble in the system maybe?

 

Small town - I take it thats bad? $50 for the part, $200 for the counrty bumpkins to figure out metric cause all they are used to at Mustangs and Camaros?

 

Or ~$50ish for the thermostat, and free labor, for doing it myself.

Still not sure it is the thermostat, though.

 

My guess is the coolant wasn't mixed properly for the sub-zero temperatures, and it froze. It warmed up in the engine when it was running, but couldn't get through the hoses to the heater and radiator. That would explain the overheating and the lack of warm air from the heater.

If you're lucky, the time in the garage warmed all the coolant up, and everything will work OK. You'll need to adjust the coolant mix to prevent it from happening again.

If you're unlucky, the engine is wrecked from overheating, and the radiator and heater core are wrecked from freezing. Hopefully, that's not the case.

 

Drained and refilled the radiator today, went out and ran it, everything works fine, heat comes from the heater, temp doesn't overheat.

So I think you are right about the coolant being too much water, not enough anti-freeze.