How Coolant and Transmission Fluid Mix, How It Affects The Vehicle, and What Can Be Done

In this video I'll go over how transmission fluid can enter the cooling system and/ or how coolant can enter the transmission fluid. I'll also go over how this negatively affects both the cooling system and the transmission. I then discuss what can be done about this issue.

A failure such as this is either caused by someone adding the wrong fluid to the wrong system or by a faulty transmission fluid cooler. And while people do add the wrong fluid to the wrong system it's far more likely that this is caused by a faulty cooler. A leak develops in the cooler allowing either transmission fluid to enter the cooling system and/ or coolant to enter the transmission.

This truly messes up a bunch of stuff. In the cooling system all of the rubber can be ruined by transmission fluid. It can also affect the cooling systems ability to properly cool the engine. If coolant gets into the transmission it can ruin the clutch packs and potentially the whole transmission. Usually a rebuild or a transmission replacement is needed. ***If the transmission is replaced or rebuilt due to this then it is recommended to flush the cooler lines to the transmission to remove any coolant so that the new transmission is not affected.***

Of course, to repair this, the transmission fluid cooler will have to be replaced. If the cooler is internal to the radiator then the radiator will have to be replaced. If transmission fluid entered the cooling system then the cooling system will need to be thoroughly flushed out until there is no more transmission fluid in the cooling system. I'd also recommend replacing all the rubber components in the system. If coolant has gotten into the transmission it is likely the transmission will have to be rebuilt or replaced. However, It's worth a try to do a thorough transmission fluid flush with a filter replacement. (this may take several dozen quarts of fluid to do properly.)

Note: this video is superficial in nature and cannot apply to all vehicles out there. A lot of the information given in the video is a matter of opinion and may not be best for your vehicle given factors unknown. Do your own research.

Images shown in video depict not only contaminated fluid but also uncontaminated fluid. Contaminated fluid with have a "milky", thick, opaque, look to it. Some coolants are red or orange. Red and orange coolant is supposed to be red and orange. But when it gets contaminated with transmission fluid it becomes "milky" and thick. Also, most transmission fluids are red or some shade of red. This too will become "milky" and thick when coolant is mixed in with it. In both cases, with the coolant and transmission fluid, the severity of contamination may vary.

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GENERAL DISCLAIMER
Barbour's Auto Help is not responsible for any damage or personal injury incurred in the process of performing any auto repairs done by you the viewer. Automotive repair is extremely dangerous. Repair your vehicle at your own risk. It is the viewers responsibility to verify all information and procedures as outlined in YOUR REPAIR MANUAL AND OWNERS MANUAL FOR YOUR VEHICLE. Owning and using a repair manual suited for your vehicle is essential for correctly and safely performing ANY repair to your vehicle. Always wear safety glasses and protective gloves and heed all instructions for use applicable to any piece of equipment you may use. Due to circumstances out of the control of Barbour's Auto Help, Barbour's Auto Help makes no guarantee that by the use of the information given in this video a quality repair will be made. Barbour's Auto Help makes no guarantee that the information provided is totally complete, synchronized and accurate. Verify everything using an appropriate repair manual.

Repair your vehicle at your own risk! Barbour's auto help does not guarantee a proper repair using these techniques.

[Terry]

Automotive Engineers: "Hey let's put the transmission cooler inside the radiator so that if it fails the coolant can mix with the transmission fluid".

Genius!

[ElastroOchoa-cqvb]

The best video of mechanic help ive ever seeing ❤🎉

[Jackiegirlone]

Wow, what a great communicator you are, this was very helpful

[maskerade]

Thank you for this very well and easily explained of what is happening and the future of parts. I unfortunately have both issues. I bought a used 2005 Toyota Sequoia and now I have to get rebuild the transmission before it fails completely.

[jacobclark]

Good point, changing all the rubber stuff .

[JeffKendallWeed]

Great video, nice work man. Helping a friend assess if she should fix coolant in trans/coolant in oil in a 200k CRV. Leaning toward letting the insurance co having the car!

[siddjay]

This became a very helpful video in just 1m & 27secs.. awesome!

[connerdux]

Thank you for this video, went to take my 1979 gmc for a cruise and popped the rad cap to find a pink mix, glad I found that before driving cause I have to drive to Ontario with it

[daltoncastro]

This video saved me from doing head gaskets on my 3100 Buick

[johnwagner]

That is a mess! Good information! TY I wouldn't recommend a trans FLUSH.... That can destroy the transmission as you know. I myself would service the transmission now, then again a few weeks later.

[FusionDeveloper]

I just realized, since there are transmission lines running to my radiator, then that means there is a chance that a busted radiator, could potentially mess with your transmission too.

[daveshanton]

Thanks for the informational video! I have a pink milkshake coming out of my 84 Chevy Caprice radiator. Thanks for the words of caution on what damage can be done to both systems.

[billymiller]

I don't normally comment on videos but great video

[pistolasnine]

Thank you so much! My car just had this issue, coolant mixed into the transmission....up for new transmission

[firdausravindar]

Thank you very much for this beneficial video on auto transmission mechanics.

[chrisharm]

Had this happen to my 2017 Tacoma, it’s in the shop now, looks like warranty is picking it up!

[zombiekller]

I have the trans oil in my radiator but am not sure how it happened I just replaced my water pump started it up an the radiator spewed out the red stuff from the radiator cap( no leak is found)

[keving]

Does anyone know if there are aftermarket radiators that have solved this problem, with better materials use?

[Braulio]

This happen on my isuzu box truck, had to replace radiator and transmission . And replace both upper and lower radiator hoses.

[arianabedi]

I’ve had my radiator blow and cause my transmission to lose 4/7 gears completely. Re did the whole radiator first was flushed over 5 times and re hosed then ordered a used transmission which I’m still waiting for. Should I be doing anything else for extra safety before I get my used one installed?