I have water in my automatic transmission. Can it be flushed out?

  1. In a word, no.  When water gets inside of an automatic transmission, the friction lining of the clutches absorbs it and dissolves the glue that attaches the material to the clutch plates.  Usually, some amount of water will come out of suspension and form white gummy masses in various areas of the unit.

Simply put, this is why the unit cannot be flushed to remove all of the water.

In addition, the presence of water will start rust forming on the ferrous metal parts throughout the unit.  The amount of water and the length of time that it is inside of the unit will determine the extent of the damage, but the resolve to the problem will be to overhaul the transmission.

There is no shortcut that will “repair” the situation!  It’s only a matter of time before the unit will exhibit abnormal operating characteristics and fail completely.

FYI, water usually gets into the transmission in one of two ways.  First, all transmissions have a vent to maintain equal barometric pressure inside of the transmission.  If the vehicle is driven through water (as in a flood) and the water level is at or above the vent, the water will cool the unit lowering the internal temperature and water is drawn inside of the transmission.

Also, virtually all modern transmissions (some were air cooler in the old days) have two cooler lines that route from the transmission to a special tank the radiator to cool the transmission fluid.  If this special tank ruptures, transmission fluid can enter the radiator and water can enter the transmission.  In this case, the cooler tank in the radiator will have to be replaced as well as rebuilding the transmission.  One of the common indications of transmission fluid in the radiator coolant is the “strawberry milkshake” appearance of the coolant.

There’s no way to give a time that transmission abnormalities will show up.  It can be as little as a couple of weeks or longer depending on how much water got into the transmission and how much it is driven with the water.

Additional Resources
Automotive Service Association article on water in the transmission

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  1. Posted April 21, 2015 at 5:43 pm | Permalink

    Very useful information. A lot of people wonder why it can’t be flushed out but your explanation couldn’t be clearer.

  2. Posted May 4, 2015 at 10:31 am | Permalink

    Great article. I’m facing some of these issues as

  3. Posted June 12, 2015 at 6:45 am | Permalink

    Just the answer I am looking for my automatic car, thanks for this.

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