2013 Tundra Platinum 5.7L - Found Oil In Radiator

Hello All,

As the title suggests, I found oil in my radiator yesterday morning. I discovered this after investigating why there was a huge mess of brown fluid underneath my truck, which I now know that it's an oil/coolant mixture from the radiator. Turns out, the small hose on top of the radiator (right next to the cap) blew off and the oil/coolant mixture spewed out and covered the front side of my engine and dripped onto the driveway. The same mixture is also inside the coolant reservoir.



Since then I have been trying to find any posts of this happening to anyone else and can’t find anything so I hope that one of you can help me. I believe I have the towing package (I have a tow button and back hitch with cable hookups) and I’ve read that there is an ATF warmer and cooler.

Reading through posts, I've learned that the transmission cooler is part of the AC condenser in front of the radiator and has two lines that go to and from the small unit on the transmission. I'm under the impression that the transmission cooler does not interact with the radiator coolant but relies on air cooling alone. Therefore, engine coolant cannot get into the transmission cooler circuit. Please confirm if I am correct or not.

Regarding the transmission warmer, there is a thermostatic valve that opens when the transmission is too cold and circulates engine coolant. Inside the transmission warmer are coils that the transmission fluid circulate through and exchanges heat with the surrounding engine coolant. In other words, the transmission warmer is the shell side and the transmission fluid is the tube side of a heat exchanger. Please confirm if I am correct or not. If this is correct, then the only way that transmission fluid can enter the engine coolant system is through the transmission warmer. Please confirm if I am correct or not. If that's the case, are there tube joints inside that the oil could leak through? Possibly a corrosion issue?

If there is another route that the transmission oil can enter the coolant stream, then please let me know.



I also thought of the possibility of a cracked block or blown head gasket, which would allow oil to enter the coolant system. This may explain why the small hose near the radiator cap blew off, due to overpressure in coolant system.

I'm hoping the solution would be to replace the ATF warmer and then flush transmission and radiator, versus an engine overhaul that I cannot afford.

Please let me know your thoughts and I thank you in advance for taking the time to answer my questions.

 

First - correct.
Second - correct.
Third - correct.


Your engine also has an oil cooler on the side of the oil filter housing that could be the cause, if it’s engine oil in the cooling system rather than ATF.



ATF has it’s distinct smell even in cooling systems while engine oil - not so much.

Try to determine which it is, and check for signs of coolant in the engine oil and transmission. I’d briefly pull the trans plug to drain a small amount of fluid into a clean container.

 

If you are able to determine that it’s engine oil, then removing the engine oil cooler for pressure testing would be a good step to take next. A rad shop can do this if you’re not equipped to.

If it’s ATF, then the warmer / heat exchanger is the only possible leak path.

 

Agree with LandPhil, process of elimination.

Check your engine oil dipstick first.


Greg

 

Thank you for the quick responses. I forgot to mention that I checked the engine oil dipstick yesterday as well. Level looked good and the color was as it should be. Guess I forgot to include these notes since my mind ruled out engine oil as the likely cause and was focused on the transmission. I will be pulling one of the lines to the transmission cooler to verify if the transmission fluid is contaminated with coolant or not.

Please let me know if you come up with any other possibilities/solutions.

 

Check the radiator over flow tank. Hopefully it's not pink! I had a transmission failure due to atf enteeing the cooling system. And vice versa.. end result was expensive. I agree with landfill. Pull the plug on the transmission. Hope this isn't your problem.

 

Some tacomas have had this happen also with the atf getting into the cooling system. What a horrible design..

 

Hi,

Will somebody please share with me the part number for the transmission heater/warmer or provide the catalog? I am having trouble finding it and have only seen the transmission cooler online. Thank you in advance.

 

Looking at the drawings again, it looks like the cooler/warmer is one unit. I was under the impression that they were separate units but I think now that the thermostat is what determines the separate functions.