Our 08 RDX was shifting badly yesterday and today I noticed a bunch of transmission fluid in the coolant resivoir and I am not sure how it got there because I don't see any info on the trans fluid going thru the radiator.

 

There’s a transmission cooler built into the radiator. This has been a problem for a small percentage of owners. Recommendations includes to not drive the vehicle to contain the contamination, do a 3x3 drain/fill of trans fluid, and a radiator replacement with fresh coolant. All this is far cheaper than driving around and possibly needing a transmission replacement. This has been one of my major worries with this car. Original coolant needs to be flushed and replaced in 10 years or 100k because it’s corrosive over time. I’m thinking of doing a stand-alone trans cooler for peace of mind after my coolant flush coming up. Hope this helps

 

well, the problem was noticed yesterday afternoon and after hard shifting this morning (10 mile drive), I checked it more thoroughly and saw lots of trans fluid in radiator but low fluid in transmission. Taking to mechanic today.

 

Don’t put too much thought into a catastrophic failure if driven at all. Some members have limped home much farther than you and did the recommended replacements and reported good outcomes. Just don’t take it on road trips or things of that nature but I’m sure you don’t plan to although a tow to the mechanic won’t hurt.

 

wel, I cant see the reason to drive a car with leaking transmission fluid into the radiator.

 

I’m sorry I’m confused. Are you agreeing with me that the less the car is driven the better? Or are you thinking that I’m telling you that it’ll be fine to drive to the mechanics? Because that’s not the case. I personally wouldn’t even start the car and get a $50-$80 tow.

 

Well, yes, agreeing. The less driving the better, but I feel angry that my wife drove it today for 10 miles and I didn't realize what was happening. Even not knowing that this must have been happening for a few days or so, has me angry.

 

Time for a new radiator. I'd recommend buying a DENSO replacement on Amazon or RockAuto.com and putting it in rather than a 3rd party.

 

Ahh, I can relate to your frustration. I’d feel the same way if I were in your shoes but you got to remember that’s your wife and she honestly didn’t know. The leak was bound to occur, it just so happened while she was driving. I definitely feel you caught it way early and the odds that things will be fine after the replacements are very high. Keep us posted.

 

yes, of course. I would love to do this myself BUT, I dont have the confidence to flush out the engine and possibly the transmission afterwards. A dear friend runs a shop and he is expecting me.

THANKS FOR THE REPLYS FROM EVERYONE.

 

well, she told me it was hard shifting yesterday. I took it out and it was fine. This morning, did it again and when she got home I saw fluid all over the coolant reservoir.

 

Just quick note - 5 years / 150k miles (whichever comes first) is the recommended change, not 10/100k (that's Hyundai's warranty). I don't mean to pick nits, but leaving coolant in the system for 10 years would be a major contributor to internal radiator failure like this.