Coolant issues.
 

Alright I'm getting fed up that I can't find this problem that I have with my 2000 Blazer. I noticed the problem about a month ago, my temperature gauge heats all the way up to 260 (takes about 5 min) it stays there for about a min or two. Then it drops all the way back down to 100. It stays there for a while then jumps back up to 260. I know the heater core is out of commission, just replaced the thermostat, and the pipe that connects the thermostat to the upper hose (there was a small crack in that before). But now on my way to work this morning the gasket on the thermostat busted. I'm at a loss and now it seems all of this is taking a toll on my engine.

Please help.

Is this the same problem before you changed the tstat? In other words the wild temperature swings. This still points to tsat, did you bleed the air out of the system? New parts don't always mean good parts.

Yes this is the same problem as before. It actually started when I changed my oil at 136k. Odo reads 137k. After I changed the thermostat I noticed the small crack in the metal pipe from tstat. Replaced that and its all down hill from there. Btw no HP when I press the gas goes to 4-5k rpm before shifting.

How do you bleed air out of system?

The way I was taught was to drain, flush the crap out, then fill with water, then flush it again using distilled water and antifreeze. Then you keep the radiator cap or whatever is highest up loose while you get the engine up to high temp, and keep revving the engine so the pump blows all the air out and fill it to the brim. Always worked for me anyhow.