Anything you put between the tank and support is still going to put unwanted pressure on the tank. The problem with the H3 radiator is two-fold:

1) The orginal composite tank material is weak and may have thin spots which are known to crack even without any pressure from the support.

2) Due to a faulty design, the lip of the radiator support often makes contact with the OEM tank and may either cut through the plastic tank over time near the neck, or put stress on the tank causing it to crack.

To eliminate the problem: 1)Get either a new radiator with the redesigned top tank or aftermarket all-alluminum radiator, and 2) trim back the offending lip from the radiator support so there is adequate clearance.

 

Over here the Hummer Dealer is the same as the GM dealer, both sold from the same location. I took it both times there, first time I think it cost me around 1000 for parts and labour. Then I had a crack at the top plastic part.
As for the Alpha, its being taken care of under warranty, but i noticed that the crack was between the metal bit and the plastic.

 

If you can't get the dealer to offer a free replacement I suggest a rebuild of your stock radiator over a new Silla aftermarket. The Silla is clearly inferior when you open it up and take a look inside. While they work for light duty operation, if you are going to tow with your H3 or drive in the mountains stick with the OEM radiator. Especially true if your H3 has an automatic transmission.

The Silla is a copy of the original design using inferior Chinese parts, and does not offer the beveled top tank. A lifetime warranty from Silla means nothing if its going to crack and not properly cool your engine and transmission in extreme conditions.

It cost me $100 for a rebuild at Mike Dana Radiator in Mesa, AZ. The top plastic tank in the center is where they all crack. Same thing happens on the Chevy Colorado pickup truck which has the same 5 Cyl engine. Their company truck is a Colorado and yes they already had to rebuild the radiator. Nature of the beast!

The replacement plastic top tank is now beveled back a bit, not so much for clearance as some suggest … but to add more strength. They have yet to see the redesigned tank crack ... time will tell.

The AC Delco replacement radiator you find on line is a mixed bag, some are the original design with the straight walled top tank. Some are cheap Chinese knockoff's using inferior internal parts. If you choose to buy a new AC Delco radiator make sure it has the new beveled top tank. Price will probably dictate which ones are the knockoffs and which ones are OEM.

Myself I chose to rebuild my original to save money and ensure I had an OEM internal parts.

 

Here are the instructions I used to replace the H3 radiator myself.

https://www.hummerforums.com/forum/h...22/#post288700

Worked perfectly.

 

Damn, now I'm paranoid. This seems to happen mostly to the 07's. Am I any safer since I have an 06?

72,000 miles no major problems yet.

 

My 2006 H3 got to 80,000 before the I noticed a "very small" leak on the ground. Yup, pulled the factory installed foam away from the front lip of the radiator and damn, I could see the dreaded crack.

No rub marks from the frame ... just a 6" long stress crack.

YMMV

 

You are not safe. It will happen.

 

Does this flat happen to every h3 in that era or only a select few.

 

It doesn't matter what year you have- 06, 07, 08 and probably the 09's soon will make an appearance with the cracked radiator. Not everyone will get the crack either, but chances are pretty good that it WILL crack on you. My advice is to either spend the money to get the radiator repaired with aluminum or brass tanks or to buy the cheapest replacement you can find and do it yourself in the driveway one afternoon. It's pretty easy to do.

 

Mine is a 2009 with 33,000 miles on it and it cracked but not at the rub point either. If it is any year H3, just look for it to happen.