After market automatic transmission coolers.

Surely there's already an OE fitment ATF cooler .... I'd be surprised if there isn't. 🤔

Unless the car manufacturer specifically recommends fitting an AT cooler when towing little will be gained and a lot will be lost (your money). If the car has a factory fitted towbar appropriate measures to cool the transmission will already have been taken so at worst it would only apply to dealer fitment, but then the dealer, too, should have taken any necessary action.

I had two Sorento's , one of the same vintage as yours and never felt the need for extra cooling even towing in the mountains of Europe. Many years prior to that I had an automatic Vauxhall Charlton and the gearbox would over heat so had an extra cooler fitted. I was never convinced that it made that much difference as the gearbox continued to overheat! Not long before I traded it in I discovered that Vauxhall had an expansion kit available which would have prevented the loss of gearbox oil!!!

David  

My early Carlton overheated too .... ☹

all auto sorentos are fitted with transmission coolers!I was unfortunate enough to have a stone puncture the cooler of my 2010 a couple of years ago.(it is mounted behind the front grill).in fact the 2003,the 2007,the 2010 and the current 2015 all were behind the grill but they are all different.

Thanks for all replys. Most informative.

What are your thoughts on changing  the at fluid ?

It can never do any harm to change the ATF. I'd pay someone else to do it though.  😉

Transmission oil can get burnt if overheated, as 'MM' says it won't do any harm. It's expensive and needs to be exact in volume though so best get someone to do it.

Get the person who changes it to smell it. 

YES...The gearbox requires a complete drain,re-fill with required quantity-warmed up to a specified temperature and then topped up to level.not a diy job.Kia,however,say that the fluid is for life!(also a certain amount of fluid will always reman in the torque convertor).Have a look at  UK sorento forum.All the advice and help you could ever need about your car!

You will never get a complete change either as the TC will still retain most of whats inside it when the fluid is drained. It maybe worth looking at getting it flushed to put your mind at rest. There are companies out there now that can offer this service using specialist dialysis type machines. 

We used to do it at work with our cooling systems with a similar type of machine.