This thread is a great example of one of the reasons why I keep coming back to this forum. I am constantly learning something new here. I would not have any idea of what to do if I found my coolant to be milky and likely would have kept driving it as long as it didn't get hot.

 

This issue scares me..my extended warranty expires in november and I'm not sure if I'll renew it. I need to check on getting an external trans cooler or possibly just replacing the radiator so I dont have to worry about it.

Sounds like a good idea to check the coolant frequently so if the problem does happen I can catch it before it kills the tranny.

 

As I understand it, like the only true prevention is to cap off the internal tranmission cooler and install an external one (which are supposedly more efficient anyway). Unfortunately, it sounds like it really doesn't matter how frequently you check the coolant, because as soon as the cross-contamination occurs the radiator/hoses etc. are done and most likely the transmission too.

 

Got my Hummer back today, one radiator, hoses, bushings etc. replacement & complete transmission rebuild, etc. later. The dealer picked up the ENTIRE bill for everything (around $4K) with absolutely no questions. I personally spoke with the AAMCO transmission shop where the transmission work was done, and was told by the manager there that his instructions from the dealer were to do whatever was necessary, regardless of cost, to make the Hummer right.

I cannot stress what an absolutely standup guy and gentleman that Judd Cook of Tampa C.A.R.S. Inc. (www.carsinctampa.com) is, and how much a gentleman he was during the entire process. When the problem was discovered last week, I simply sent Judd a text and his immediate reply text was "don't worry, I'll take care of it." Although I did worry, Judd absolutely took care of it. I doubt that I'll ever purchase another vehicle again from anyone other than Judd.

Now, to avoid this ever happening again, I am capping off the radiator and having an external transmission cooler installed next week....

 

Ok, can someone please take a step back and explain whats happening here? So there is a transmission cooler within the radiator, correct? This transmission cooler can go bad allowing transmission fluid to leak into the radiator?

How do we know if we have a problem? Does it drive funny? Does the coolant color appear different?

What does it mean to "cap off the internal transmission cooler/radiator"? How much does it cost to "cap off the radiator" and install an external transmission cooler?

 

First question, yes. There is a mini radiator for the trans fluid(so to speak...) inside the normal raditor for the engine coolant. That mini raditaor or its lines within the normal raditaor can fail (fracture) causing the trans fluid to mix with the engine coolant (anti-freeze).

While this won't do much damage to the engine coolant, it can do substantial damage to the transmission. The transmission fluid is designed to lubricate as well as cool the trans and it doesn't take kindy to other fluids mixed in...read bad ju ju.

How will you know? Either you notice the fluid in your radiator has changed color (cause you checked it often...) or the trans starts to act up (which likely means substantial damage has already been incurred by the trans...again, bad ju ju)

Options? Looks like you could check your radiator fluid regularly and if you notice the color change, take to a trans shop or dealer for repairs...hopefully only fluid replacement and repair the leaking "mini radiator" in the normal radiator.

Oooooor, have an aftermarket trans cooler installed. Preferred method.

ANY transmission shop or even the dealer can install a trans cooler. It will be more efficient that the stock version and zero chance of the fluids mixing....

Original set-up....


Aftermarket trans cooler "by-passes" the stock radiator all together..as well as cool the trans fluid MUCH better than the stock unit. A real plus if towing...cool trans fluid is your friend....its not a big deal to cut into/splice new cooling lines to an aftermarket trans cooler.

 

This is what it looks like when Dex-Cool mixes with tranmission fluid (i.e., when you know you have a problem): http://forums.justcommodores.com.au/...look-here.html

As you can see, the mixture literally looks like a strawberry milkshake. I wouldn't count on an explosion like the car in the link though - my problem was nicely contained within the coolant reservior and only discovered when I had the oil changed and fluids checked.

As far as cost, external tranmission coolers seem to run between $50 and $150, and then add hoses, etc. and labor if you have it done at a transmission shop as I will. I'm not sure if this will void a factory warranty if you have one, but Hummer and warranty companies should pay owners to have it done because it eliminates the risk of a major [expensive] repair if the transmission cooler does fail (although the warranty companies probably have exclusionary language for losses caused by contamination of fluids).

It seems to me that given the potentially catastophic consequences of coolant contaminating the tranmission fluid if an internal cooler leak exists, an external tranmission cooler is a small price to pay for reassurance that this will never occur again.

 

easy610, flbassjag

Excellent information, thank you for the breakdown and explanation.

Tomorrow morning: start shopping around for prices.

 

is this something that normally happens in all h2 s??