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Overheating during sub zero temps?

The Chad

The Chad

New member
'01 GTP with 163k. Three weeks ago, during an absolutely freezing, sub-zero temperature morning, I wasn't getting heat into the cabin. A few minutes later, it overheated. So installed a new thermostat and was good to go.

But last Tuesday was another sub-zero morning, and guess what? It happened again! No heat was getting into the cabin and it overheated. So I shut it off, sitting along the road to cool down. After 5 minutes sitting there with the engine shut off, I heard a "tunk tunk tunk tunk" sound from the engine, the sound of coolant surging. Like something finally thawed out and allowed coolant to flow? I fired it back up. Miraculously I had heat again and it was no longer overheating.

So... Did I install a bad thermostat a few weeks ago, and that's why it happened again? Or is there something else I'm not realizing?

It never did this before, pretty strange. I don't want it to happen a third time. Too cold to be sitting along the road! :th_laugh-lol3:
 


Could your coolant system be frozen? If you don't normally get that low of temperatures and you haven't tested your coolant recently, I could imagine the system freezing and not being able to flow. Once your engine was running it thawed the coolant and allowed your engine to run normally again.

Buy a little coolant tester tool and see what temp your coolant is safe for.
 
My guess is also the coolant. Prolly slushy or worse, solid in places. Either don't have coolant with adequate temperature tolerances to begin with or your coolant is just a few yrs old and loosing it's tolerance. I would change it or at least add some fresh stuff to avoid the radiator cracking.
 
change your coolant before you crack the block. if you get lucky it will only pop a freeze out plug.


being its cold out, id pull the lower rad hose off, drain the rad and refill it with 1 gallon of full strength coolant, then top off with water.

run the car for a while so it all mixes together.

or flush it and use green coolant if its not already green.



how to flush the coolant.


remove the t stat, put the t stat housing back on, take the upper hose off the radiator, then push it down to the ground to a bucket or let it fly.


get your garden hose out, put it in the rad turn it on, then fire up the car, let it run till clear water pumps out the top hose.


then turn the hose off, run the car till no more water comes out the upper hose. then turn it off.


put your t stat back in, with new gasket, the upper hose back on.


now take 1 gallon of full strength green antifreeze, not the 50/50 crap. ( parts store cheap green is fine to use) dump the whole gallon in the radiator, fire up the car, fill the rad with hose water till its full. top as needed till its ready to be bled of air. it will burp and take coolant as the water in the block warms up the t stat opens up for a few seconds till cold coolant hits it and it shuts again.


now to bleed the air out, let it idle rad cap off till the fans turn on, (when the fans are on the temp is over 195 deg, the t stat is wide open) then open the bleeder screw on top the t stat housing a few turns till a steady stream of coolant comes out the hole, shut the screw, top off the rad. cap it.


done.
 
Similar to what scotty said, your biggest risk right now is cracking your block. That would be a serious problem. If it were me (not that this is correct), I would drain out about a gallon of coolant and refill with full strength. Warm up the car to ensure the coolant mixes well and then use a coolant tester tool to see what your safe temp is. Repeat if your safe temp is still not met.
 
the rad only holds about a gallon. i just siphoned mine out with a thin hose to a gallon jug. if you pull the hose off, what ever drains from the engine is just icing at this point lol the more that comes out the better in this case.


remember if your coolant is that brown crap, only use dex coolant too. unless you flush it clean, then you can use the good old green stuff.
 


i had a 97 gtp once and i had a problem with it overheqting when it was super cold out couldnt figure out what it was for the longest time but after i let it cool down for 5-10 minutes it always be fine again. it ened up being a bad hose n it was pinching off under pressure. just a thought
 
Which hose was pinching? Interesting it only happened when cold.

Update: I'd drained some of the coolant and added full strength to mix in. I'd replaced the elbows a couple months ago so it had fresh coolant then, but draining some of that and adding full strength seems to have done the trick. This morning as 0 degrees and the care was fine.
 
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