What is it with the Blazers and possibly with the *-10'* that the radiator always cracks just on the other side of the tank behind the upper hose? My Blazer is on its 3rd one now. Well, 2nd new one. 3rd one came from the junkyard. This crack always appears in the same spot. Directly infront of the upper hose inlet. As of now, I can only speculate that the hot coolant hits this part of the plastic and makes it so hot, then it cools down. After time this ends up cracking.

I'm wondering if a cooler thermostat would help things, or even maybe drilling a small hole in the thermostat so that the warm coolant is always in contact with that part of the radiator and won't cause thermal shock.

Thoughts, ideas people?

Your more than welcome to share your experience with these GM setups, even if its on Silverado'* etc.

im not much help, all i can offer is ive had alot of vehicles, different vehicles and have had alot of them go but never there. if the tank cracks its always been at a fitting for the hose or trans cooler never on the other side. ive had some tanks leak from where they attach to the core. and i just go to autozone and get the cheap whatever and thats always lasted longer than i owned it.

the only things i can think of is check the cap is the right pressure, and the upper hose isnt putting stress on it somehow like when the hood closes or something. other than that should be the same design wise as the sbcs i have and havent had a problem

Wow I can't say I've ever seen one do that, must have something to do with the heat cycling over the years like you said though. Drilling a hole in the stat may help it live a longer life.

Well, that'* what I'm hoping for.

IMO the hole in the thermostat wont help with the problem.

Care to elaborate?

IMO, it'* not the shock of the thermostat opening that'* causing the cracking. I believe its the continual flow of the coolant, at its highest temperature, taking it'* toll over time.

Coolant doesnt flow continuously. Only when the thermo stat opens.

Understood, when its running at operating temps - it'* continuous.