Today (and yesterday I guess... didn't drive anywhere) we finally got hit with some cold weather. -20C (-4F) this morning and my car started up (didnt' sound too healthy, but considering how cold it was didn't think much of it. I let it run for a min or 2 as I cleared the snow off of it, and it seemed to be running okay.
I drive down the street, turn the corner, and just as I'm trying to go through the interestion the car stops and DIES. I try to start it but it wouldn't crank over. I pushed it back out of the intersection and pop the hood... damn, the coolant in the reservior looks like Slush Puppy! I don't remember fully, but I think the upper rad hose (from the t-stat) was kinda hard from frozen coolant aswell.
Anyways I try a few more times and it finally starts up again. I left it in D and kept my foot on the gas (and the other ready on the brake) and flipped it in Neutral when I got near other intersections. My drive to work is only ~1.5miles so I wasn't overly concerned about it having problems, I just kept my eyes on the guages. As I turned onto Edward street (where my work is) the temp needle started climbing FAST. I quickly rolled into the parking lot at work and shut her down as the needle got near the red zone.

It was still blowing ice cold air in the car and my windshield all iced up. Popped the hood again and the coolant in the reservior hadn't really moved much.
Let it sit for a few min and when the engine cooled down a bit I pulled her inside the heated washbay to unthaw. Using a coolant guage it read that mine was only good for -10C

my stupid fault from topping it up with too much water back when I changed the heatercore. I drained a gallon of my watered-down coolant mixture and dumped in another gallon of full strength AC Delco green coolant, I'll have to check tomorrow what % the mixture is good for now, but hopefully it shouldn't have this problem again.
So lesson learned... make sure you have proper antifreeze/water %, especially if you live in the North!!
Since it is suppose to be cold tonight again I plugged in the block heater (don't know if it even works) and added a bottle of gasline antifreeze to the tank to make it run better.