Emforce if you keep searching you can find a radiator for under $140 delivered and even if you are a novice mechanic, you can do the radiator yourself and save $250. I did the radiator, thermostat, new external trans cooler and replace my Hid lights today in under 3.5 hours. Granted I did have air tools but the radiator isn't a hard job at all. I would recommend removing the hood completely. Makes the job much simpler.

Luke - thanks , but too late. I already ordered a new radiator at about twice that amount - mostly because it is local and has a lifetime warranty (in case there is a fit-up problem). A question - why did you get an external trans cooler - I thought it was internal to the radiator ? Any other helpful hints - I thought I read you should use silicone thread lube/sealant for the connections - did you do this??

I also decided to also get a high performance exhaust system (magnaflow) as long it was in the shop - and have nerf bars coming also so I can get in .:D

Trans cooler is internal but sometimes the internal trans cooler fails and ends up taking out your transmission.

I didn't use any Teflon tape for the threaded connections to the radiator if that is what you are insinuating. No leaks as if yet.

Nice pickup on the exhaust. In a few weeks I'm going to fix the exhaust leak on my h2 by replacing the stock manifolds with shorty headers and arp bolts.

Any other advice would be to get everything serviced like oil, etc.

What are the things to look for to check if radiator / trans cooler is still ok? I am planning to get a 04 H2.

Thanks in advance!

I guess the obvious things would be to look for trans fluid floating on top of the water in the radiator/surge bottle, and check the trans fluid for water/anti-freeze. If your new Hummer has not had the radiator replaced and has over 100K miles you may want to consider replacing the radiator proactively as it is not that awfully expensive and may save your tranny (a lot more expensive) - at least that is what I did.

Also your temp of your trans and radiator can be a good indicator as well. Like emforce said do it proactive and save yourself a bunch of money and headaches. You can find an aftermarket radiator and external trans cooler relatively cheap. I installed my radiator and external trans cooler in a few hours. If you tackle the job yourself, remove the hood. Made it much simpler

Guys you need to search info here and the other Hummer forums.


H2's have a stock external and internal tranny cooler. You are correct on the internal failing and taking out the tranny. However you can bypass the internal cooler and just use the external. Some people have been swapping their external cooler for aftermarket after bypassing the internal. However some have said their temps are very low and have hard shifting, etc. That's where the internal helps with warming the fluid up.


So you have options.


-Bypass the internal cooler and leave the stock external
-Bypass internal and install an aftermarket external
-Leave everything the way it is


Hope that sheds some light!

Well, you forgot the 3rd option - replace the radiator with a new one. Replace the radiator cap with one with a sacrificial anode and it will be as designed and should last 10 years.