Radiator Warning!!!
 

My 2006 H2 with 100,000 miles just died because the transmission cooler inside the radiator leaked transmission fluid into my antifreeze.. The items
now replaced are transmission, trans cooler, water pump, all hoses, radiator,
thermostat,overflow bottle, etc..... I found a very nice all aluminum radiator from shepard autoparts for $150 that is a direct fitting unit and I dont want anyone else to go through this a_ _ pain. If it could happen to me then yours is no different. I serviced my cooling system regularly with 50/50 mix....

Just curious, were you using Dex-cool for your antifreeze?

Man, I have heard of a couple radiators letting go at a bit over 100K. Mine is a 100K exactly right now. Bought it used a year ago. I never got maintenance records so I don't know if the radiator was ever changed.

Is there a manufacture date on the radiator somewhere??????

Are other members proactively replacing radiators to avoid this. If I am correct, other GM trucks have this same radiator type and when I called the local GM dealer/repair shop...they said they have not performed many types of repairs due to the inner transmission cooler leaking into the radiator fluid or vise-versa.

So I am really unsure what to do. Suggestions? I am concerned over something that has a low chance of occurring? I feel for inputamech...but don't want to replace a radiator just for the hell of it either.

Reply
 

Yes I was always using Dexcool..... I figure $150 is cheap insurance to save
either your engine (because the oil cooler is in the left side) or your transmission (cooler in the right side).... I only mentioned it because it is
expensive and painful if this happens... I figure if a radiator went 100,000
miles it is worth changing anyway.... The rubber gaskets that seperate your
antifreeze and the transmission fluid get hard over time and wont last for ever.

I wouldn't say this is a common problem that happens to the 2's but it is well known. Most people will cap off the in radiator tranny cooler and just add a larger external cooler and be done with it. That is obviously before anything bad happens.

I guess that depends on what you mean by common. If it's an issue everyone is aware of in my book that makes it pretty common. I had to deal with it and the dealership did all my repairs and service. I was just driving down the highway and suddenly started to loose power. I limped to a chevy dealership and had to have my ride shipped 180 miles home to have exactly what the OP had to have done. It wasn't cheap and if it had been any other car I would have just sold it for scrap on the spot.

Well, I am back up and running.... I had a bearing in my transfer case that was making
metal so I rebuilt that as well... The worst part of the whole problem, besides the expense, is how do you get the transmission fluid/glycol sludge out of your engine??
I used Simple green cleaner. I diluted it as it says and flushed the engine 2 times then
rinsed 3 times with water (driving 20 miles in between) for you "Do it yourself types"
and it seemed to do the trick... Time will tell. Good Luck to All

I believe the radiator heat exchanger for the trans cooler lines is there to bring the trans fluid up to operating temps in colder areas and not to cool it. Living in the south, I don't need it. I can't remember off the top of my head whether I bypassed it on mine or my wife's, but will make sure to bypass it on the other one now. It's definitely worth the ounce of prevention. Especially since my radiator needs to be replaced due to coolant leaks. I also installed dual trans coolers on both H2's. Mine running 40" tires is harder on the tranny than normal even with gearing changed. After doing this, I was able to pull my trailer up the mountain passes and not even get to 150 degrees trans temps.

I spoke to a very good and trusted private mechanic. And they have certainly heard of this condition and said with 100K miles, it would be well worth the price to bypass the internal and install an external transmission cooler. I experience pretty cold winters...so they said they would mount the cooler up against the radiator so that some heat is still transferred on cold days. I am not sure why, but on cold days my tranny temp guage usually never even registers. On hot days it does.

I asked if I was just being paranoid about my radiator failing and ruining my tranny...they said they see it and a small investment now would save $3500 or more on a ruined tranny. Because you would not know the internal cooler failed until it was too late and the transmission would be ruined or contaminated.

So, I am getting an estimate as I don't really want do it myself and they know exactly what to do. When I was younger, I would not hesitate to do this myself...but as I get older....my time and energy is worth more to me. I have had this little worry in the back of my head about the radiator...so it will be good to put this worry to bed once and for all.

Might want to reconsider
 

Here is a thought about just adding a transmission cooler and not replacing
the radiator... The engine oil runs through the left side of the radiator and
if that cooler fails you are rebuilding your engine.. Most people dont replace
the radiator until it fails but when the price is $150 for a radiator plus antifreeze you should be changing anyway at some point it seems to me to
be a no brainer... Thats why I started this thread... On the H2 changing the
radiator can easily be done in 2 hrs...

This is the first I have heard about the oil cooler running through the radiator as well and possibly failing.

Maybe it is best to simply throw in a new radiator and call it good for another 100K. Hell, I dunno what the freak to do!

I have a new trans cooler to do the bypass but now I think I'll order a new radiator and replace it also before anything happens.

I just replaced the stock radiator on the wife's H3 due to the known issue with the top of the plastic tank cracking. Stock tank lasted 110K miles so hopefully the replacement will last just as long if not longer.

Double tap

"Yes I always use Dexcool" figure it's cheap insurance. against what ? not going another 100k?

Right there can be your problem, it is well known and documented this stuff can be corrosive!!!! The manufacture I used to work for used it for aprox 2 years in the equipment they sold. Well most everyone of those trucks ended up with either scaly build up in the engines & hose's to eaten apart rads!!!

It was even thought this crap was capable and responsible for the rash of 4.3 GM intake & gasket failures happening in the late 90s (along with every other GM engine in the time period with plastic intakes)

I would love to cut some of these failed rads apart, I would beat the farm the coolers were / are eaten thru buy dexcool.

I agree 100%. Dexcool ate the intake gasket on my gmc pick up and my blazer. My mechanic is dead against dexcool and flushes it out and replaces it with normal antifreeze. We have had it done on the wifes yukon. I need to get it done to the h2.

My h2 has external coolers on the rad. So I,m thinking the PO had it bypassed? For $150 I can't think of cheaper insurance to replace the rad. Compared to the thousands when it goes south.

On the todo list. Thanks for posting this.

My new radiator is going in Monday and then I can cross this off my list. At 100K now, should be good for as long as I own it...since I drive only about 5k a year.

Reading this thread makes me wanna replace some parts now. I have a 07 h2 with 70000 miles. So what exactly do I need to buy to fix this problem? I have a friend who is a good mechanic so it shouldn't be to hard to replace.

Start by flushing the coolant system if you have Dexcool in it...like I mentioned in my above post if I could examine these rads with the internal cooler failures I bet the we're eaten thru (corroded) which led to there failure...

So do you guys run normal green antifreeze through it then if your not running DexCool?

I would doubt by now that anyone has a factory warranty in effect but running regular antifreeze as opposed to DexCool I'm sure would void any warranty on those parts that may be affected by the antifreeze. Mine is an 06 but I only have about 60k on the odo so I haven't seen any issues. At the same time I do plan on using a separate tranny cooler at some point just to prevent any failures down the road.

So yesterday my new radiator went in. My new water pump as well (was leaking out of the weep hole or somewhere thereabouts) went in as well. I had a NAPA service center do the repairs as I just did not feel like messing around with all that coolant and mess. It was a pretty expensive day...but a bonus was that the parts & LABOR are covered for LIFE. That is a pretty good feeling that I never have to endure the cost of a radiator or water pump again! All-in-all, I guess it was worth it.

Heck ya I could have done it myself for half the cost, but I am getting to the age where I don't really enjoy doing some repairs....like radiators and water pumps...

Anyway feels good to have this done and I am ready for the next 100K miles!!!

As another bonus, it is nice to come out in the garage and see no drips/leaks on the floor coming from my H2. Nice!!!

It was time anyways. I replaced my water pump,thermostat and radiator at 100k also.

Im at 154k and its about time for me to do the radiator and im also doing the water pump and may replace the ac condenser too . Was thinking of replacing the stock radiator with a becool but that may be a bit too much ...

Final Conclusion
 

Well people made me currious so I cut open my failed radiator and here is what I found... I see no signs of corrosion on the failed transmission cooler
inside or out... There is a split about .08 inches long on the backside of the
cooler opposite the intake port which accepts the fluid from the transmission
pump... The case is slightly deformed outward which seems to suggest it is
simply a pressure over time situation and possibly impurities in the fluid that
broke the cooler and caused the problem... My conclusion is that the cooler
reached its designed service limit and supports my opinion that radiators should be changed between 80 and 100 thousand miles... Thanks for all the
replies and I hope no one else goes through this..... Cheers

Inputapmech, Thanks for starting this post. It was your story that FINALLY pushed me over the edge and convinced me to do it. I have not given my radiator/water pump a second thought since replacing them 2 weeks ago.

I love my H2 so damn much that it is worth it to me to do some preventative maintenance. I get more compliments than guys who just spent $55K on a brand new truck. Hummers H2s just have that "cult" following and everyone but the extreme tree huggers think they are cool. Freakin love my H2!

My mechanic also confirmed that it was the original radiator in my H2, so that simply confirms to me that it was a good idea to replace it. No regrets at all.

Thankyou
 

Thankyou Sir for your kind words.. My only desire was to raise awareness
of this costly problem and hopefully assist others in avoiding the thousands
of dollars this problems can cost as it did to me.. I love mine as well and wish you well........

My 2005 H2 has 120K miles on in and after some research I decided to change my radiator too. Did it myself. Wasn't too hard . . . I went slow. Took me about 3 hours but I saved a lot of money. Changed the two hoses while I was at it.

Nice work PaulB. Feels good knowing that is done!

Love this place. Doing research and one of my coworkers who has the same vehicle 03 h2, his radiator just exploded trans fluid all over the place. I got worried. I bought mine with 77K on the clock and noticed two small radiators in front of my main radiator. You guys just confirmed that I dont have to worry as the previous owner took care of this. I love my truck as well. Tried to get a personal plate TREEHGR but one of you Hummer Heads took it. :)) Hummers Rock!

Is everyone just using an OEM rad? If not what brand is the best for replacement? I've got an 05 and I've been doing all the 100K maintenance lately.

Great information, many thanks!

I'm going through my 2007 H2 and came across this last night. So I'm assuming the small cooler in front of the radiator is an oil cooler then? I'm original owner and I don't remember adding anything to the cooling. I attached some pics. Also, I ordered the two volume repair manual in November from ebay, still don't have it (on Backorder). So I'm a little in the dark until it arrives :confused:

If your the original owner and you haven't added it. I believe that is your power steering cooler.

Mine has two coolers (03). Power steering and trans. The trans internal cooler was bypassed and made external by the PO.

I also check my 2003 Hummer H2 and found that there are two smaller coolers or radiators in front of big main radiator. One cooler or radiator is smaller and second one is the smallest. What are these smoller radiators for? I didn't add any radiators by myself. May be previous owner did it but that time I purchased the truck mileage was around 100,000km. Any ideas?

most likely they caped off your internal lines in your radiator. transmission cooler and engine cooler lines.and added these externaley. these are just my thoughts on this.

So do You think that previous owner did good job for me and brought outside those transmission cooling lines?

I've seen a few people post on here that the internal trans cooler let go inside the rad and flooded there trans with coolant and destroyed it.

Personally I would rather it be external.

So,is the originally installed transmission cooler should be inside the main radiator? I've got from previous posts that some guys had troubles with that design, so that's why many people put transmission cooler outside main radiator to prevent from breaking it down and and polluting main big radiator or wise versa.So what kind of coolers are outside of main radiator in my case: transmission cooler and oil cooler?

Since I'm running the factory setup on my 2007 H2 and I have about 120k miles, I think I will do the external trans cooler. I would also like to change the radiator to a new one that doesn't have half of it used for cooling the trans fluid. I live in AZ and the more cooling the better.
I've read a lot this past week about Dex-cool and the corrosive properties. The plus side with Dex-cool is that it lasts longer (about 75k miles) than the conventional coolant (30k miles). You can change out the fluid, but you need to do a really good flush to get the dex-cool out. Then you need to change the coolant every 30k miles. There is also a possible class action lawsuit vs GM concerning the Dex-cool corrosion problems. You also need to wait until you are out of warranty to do it, as I'm sure it will void it if you change coolants.

I believe one is a transmission the other is power steering. A member (MadMayo) stated that is what he has. Not sure if they have external oil cooler for the engine? I guess if you have the money anything is possible :D