Engine Overheating Issues

I would check the small hoses that go to your surge tank. If they are plugged they won't allow steam to go back to the tank causing large air pockets in the cooling system. Air in system will not allow t-stat to open.

Make sure your 2 small hoses to the surge tank are not plugged. They keep steam pockets from forming in the cooling system. T-stat won't open if there is air behind it.

I have just taken both hoses off, blown them out, & reinstalled them. Both were clean, just a little damp. I did also remove the thin pipe going to the t-stat housing & check that one for blockage too. I may try bleeding the cooling system again tomorrow.

Update: Flushed heater core multiple times in both directions, put an ACDelco thermostat in, & put old coolant pump back with new seal, just in case new pump was faulty. No change in operating behaviour. Found a hole near the top of my rad today, but unsure of whether it was there the whole time, or if I blew my rad yesterday when the car overheated really bad (really bad like, I turned the car off while driving to work & rolled to a stop on the shoulder, car was making a thumping sound even with the engine off). Running to Canadian Tire tomorrow for a new rad, praying it solves the issue.

Well, I pushed it a bit too hard during the last cold snap while I was rushing to work to pick up a shift. Blew the rad. Aaaand, guess who's fault it was *drum roll* ................................ .................................HEAD GASKET. The logic: It wasn't so bad / noticeable during the summer because it didn't have to idle long to reach operating temperature for the t-stat to open, so there was less time for leakage from combustion chamber to accumulate near thermostat. Last week though, when it dipped to -50, the car had to idle for about half an hour to get up to temp & it took some effort to get the t-stat to open (had to wait for it to go a couple of ticks higher than normal, turn engine off & watch temp continue to rise to about 3/4, then it would settle to about the 3rd tick above normal, start car again, then rev & hold at 2000RPM for ~5 sec until heat got warm & temp settled down. I am thinking, air (or exhaust) keeps accumulating near t-stat, making it difficult for it to open. If I do the above procedure, every time before I use the car, it never overheats on the road anymore & coolant doesn't boil over. I do still have to add some coolant every few days - once a week though. But, at least it's not boiling over. Will have all seals/gaskets done as soon as I can cough up the $1500 for Canadian Tire to do it or if the car makes it until summer when it's warm enough for me to think about taking my engine apart.