Hello folks, I have an 02 Blazer 4wd 4.3L auto. Recently the weather went hot around here, high 90's and low 100's.

Anyway, my wife was heading up a long grade on eastbound 50 in CA when the truck began to overheat pretty badly, even short trips between stores got the temps uncomfortably high. ENough so that even the trans seemed to start slipping a little.

SO, I have her come home and I check the coolant, its full, of that DEX COOL **** and it looks filthy..The cap is also heavily corroded and gunked up!

I started the engine and revved it a little with the cap off to try and coax some potential bubbles out, and when done revving, it just shut off, 3 times, key on in park.

WTF is going on here???

 

I would say the thermostat is stuck shut. Mine got stuck open and was very dirty from that dex-cool. Cheap and easy to fix...try that first. If it works..I'd get your coolent flushed

 

Replace your radiator cap WITH ON FOR YOUR TRUCK, not just a generic. The generic ones may keep to much pressure in your rad or not enough causing your cooling system to not function. Also get rid of that dexicool junk.

 

Definitely sounds like a thermostat. Get it replaced, and do a line flush to get out as much of the gunk from the dexcool as possible. Then get a new rad cap if it's all corroded.
Fill it back up with something other then dexcool and see how that works.

 

Get the Stant safety cap and a new thermostat. The radiator cap likely failed, allowing air into the system quite some time ago causing your current issues. Flush the system out and then add the new items (cap & t-stat).