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Old 02-09-2014, 06:13 AM   #1
Join Date: Oct 2013
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DEF Freeze up

Just wondering if any of you have had this happen this year, while trying to get out of the cool weather. Be safe out there and enjoy the day.

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Old 02-09-2014, 06:20 AM   #2
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We had to spend time in Northern Illinois last month, with temps over night of more than 20 below and highs of less than zero. We had no problems with DEF freeze up. But make sure you have the winter blend of diesel in your tank or put in additive to prevent gel. If you fill up in south, and travel north, that is.

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Old 02-09-2014, 07:17 AM   #3
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The following is from a Q&A site about DEF.

Q. When will DEF freeze ? A. This 32.5% solution will begin to freeze at 12 deg F (-11 deg C). At 32.5%, both the urea and water will freeze at the same rate, ensuring that as it thaws, the fluid does not become diluted, or over concentrated. Unthawing will not cause harm to the product.

Q. How do I keep the DEF from freezing in the tank of a Truck?A. SCR systems are designed to provide heating for the DEF tank and supply lines. If DEF freezes when the vehicle is shut down, start up and normal operation of the vehicle will not be inhibited. The SCR heating system is designed to quickly return the DEF to liquid form.
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Old 02-09-2014, 08:01 AM   #4
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That's the same information I got from GM for my Silverado.
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Old 02-09-2014, 08:32 AM   #5
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Originally Posted by DavisK View Post
That's the same information I got from GM for my Silverado.
Yup it is the same for all vehicles that use DEF. Im sure GM and others do it but Ford will reverse the DEF pump to clear out the lines of all DEF after the engine is shut down. This will keep the lines from having frozen DEF in it and the DEF will not cause line damage. Once the DEF is thawed in the heated tank, the lines are then refilled for normal use.
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Old 03-06-2014, 11:23 AM   #6
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Good questions, answers, and observations on this post.

I'd like to add the following:

It is important not to overfill the vehicle DEF tank in very cold weather, since DEF expands (like water) when it freezes. An overfilled DEF tank that freezes will likely damage the tank.

The F350 pump back system (and other trucks) serves several purposes: The primary reason is to purge the line at shutdown to avoid boiling off the water in DEF (67.5% water) and leaving solid urea residue in the line/injector which would plug the doser. It also prevents freeze up damage as jamesrxx951 noted.

Jugs of DEF will freeze solid at around 8-10 degrees F. Since most jugs are filled to the top, they burst the seal and cap off when they freeze. I've done this intentionally as part of our company's research. The resulting mess when they thaw is not enjoyable. Don't store retail jugs of DEF in temperatures under 10F.

In the range of 10-16 F, DEF will begin to precipitate urea crystals. I've witnessed this and the process is completely reversible. We've tested DEF after freezing, and the purity and other factors are maintained PROVIDED all the urea is re-dissolved.

Please consider our company a Forum resource for all questions about DEF and DEF equipment. We have all the ISO specifications an a vast library of information about DEF and your clean diesel truck. You can find us in the vendor section under Five Star DEF.


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