I think I looked all over for it. Does the H3 have a radiater drain petcock? Is there an engine drain plug?

I

 

There is none. With coolant service intervals much higher now I believe they've done away with them or so that's how I understood it. If you are doing a drain/flush of the coolant system, you might want to check this thread out:
https://www.hummerforums.com/forum/h...pletely-23791/

 

After taking a second look, I just realized you started the thread I posted above to try to help out. Sorry, didn't put 2 & 2 together until now. Doc explains there why the H3 doesn't have the radiator drain plug though and how to change the coolant.
Hope your thread helps... lol

 

How about the 5.3L? Does it have one? I'm going to need to wrap up all of my 50k service soon.....

 

I'm unsure about the V8 application. Any Alpha owners out there change their coolant yet?

Also, might want to check what's talked about in this thread while you're changing the coolant/poking around the radiator:
https://www.hummerforums.com/forum/h...-leaked-21184/