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