DEF Update

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Going through some content support tickets last week I came upon one where the customer wasn’t sure where to find the DEF tank filler. I thought that’s a pretty silly question then I remembered a situation my wife and I were in one day. We were in the Marine Corps Exchange and came upon a table with these new things called iPads. We looked at them and had no idea how to use them. The next thing we know a little girl about 5 stands on her toes to reach the table and showed us how the iPad worked. Her little fingers were all over it showing us everything about it. Moral of the story is I should never prejudge a question no matter how much I know or don’t know.  As DEF is now a way of life for us I thought an update may be in order.

The DEF tank generally sits next to the diesel fuel tank. The filler cap is light blue for easy identification. Depending on chassis layout the tank may sit by itself. Due to various OEM configurations it may be setup either way. Once the tank has been installed by the OEM by law it cannot be moved or relocated.

As DEF is highly corrosive, take precautions that it does not come into contact with any surrounding parts. Special care is required as this may contribute to a malfunction, especially when DEF comes in contact with electric wiring or connectors. If DEF gets onto a component, clean it off immediately, using a rag moistened with hot water; if required, rinse it off with hot water and dry completely. Prior to any connector installation, visually inspect to ensure that no signs of corrosion etc. are present.

If DEF tank level tube on DEF tank is deteriorated and brown colored, it is evidence of diesel fuel possibly filled to the tank. If DEF pump main filter indicates a yellow slime, it is an evidence of biodiesel fuel possibly filled to the tank.

When handling DEF follow these safety precautions:

  1. Wear appropriate protective equipment as required. Do not use fabric gloves such as cotton work gloves as frayed fiber may enter DEF.
  2. To prevent the entry of dust into DEF tank, clean filler port and surrounding areas prior to filling with DEF.
  3. In case of contact with eyes or skin, immediately flush affected area with running water for a minimum 15 minutes and seek medical attention if needed.
  4. When disposal of DEF is required, handle it same as industrial waste material. Do not dispose of DEF and empty containers into the environment.
  5. Service life of DEF is dependent on temperature. DEF must be stored temperatures of 86 degrees F (30 degrees C) or less.
  6. DEF freezes at a temperatures of 12.2 degrees F (11 degrees C). Do not store DEF at a temperatures less than 14 degrees F (-10 degrees C). Once DEF freezes its volume increases and may damage the storage container.

We have just touched on a very small aspect here in the usage of DEF. For more safety and system diagnosis and repair information consult Mitchell1 Truck Series. Information concerning DEF is generally found in exhaust articles.

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About the Author

Bruce Cansler

Bruce Cansler started his automotive career in 1973 as a technician for Datsun. He retired from the U.S. Navy as a Seabee Construction Mechanic with 20 active years of service and 10 as a reservist, then spent time working in Ford, Lexus and Caterpillar dealerships. Bruce has obtained ASE certifications in both cars and medium/heavy trucks and has worked with the Commercial Vehicle Group at Mitchell 1 since 2009.