Engine ran cold, then overheated?
 

So yesterday I let my truck (93 sierra 350 TBI) heat up for 20 minutes since it was -25 celsius with windchill, the drive to work was unusually long at an hour. Yet the temperature gauge didnt move up at all and there was NO warm air in the cabin at all, which made for a very very cold start to the day. Then on the way home from work, about 5 minutes into the commute the trucks temp gauge was climbing insanely fast and then it overheated and spilled coolant. At this point the overflow reservoir was full, coolant is pretty much brand new, engine only has 10,000 kms on it. I'm hoping that this is the thermostat? any help or advice?

sounds like a bad thermostat to me.

I agree - sounds like it stuck.

thats what i thought, picked one up today and will put it in tomorrow and see how that works

The thermostats have the little pellet that melts when it reaches a certain temperature to allow coolant to flow correct?? If so, my logic tells me that when you parked it the night before the thermostat froze open from cooling down too quick, then you drove it to work and it was able to close again, though messed up and deformed, causing it to not melt at the correct temperature or at all...?

This is just me doing a little bit of theorizing

so today i pulled out the old one and it was FROZEN, so i put in the new one and it runs better than before. since it was frozen, i am thinking that the antifreeze mixture was a little heavy on water, so i am going to avoid driving it until i flush the whole system and replace with fresh coolant.

thanks for all the input

Instead of completely removing all the old antifreeze and such, I personally would just syphon as much of the current stuff out of the radiator as you can, then just fill it back up with straight antifreeze, this should help to skew your ratio. You can also purchase a device that will tell you the freezing point of your antifreeze. I'd keep skewing the ratio until you get a freezing point that is at least 15 degrees below the lowest temperature you experience is.

freezing point was at +12 celsius, PO must have had run a strong water mixture. all in all its now fixed

Great!