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Hello fellow truckers, looking for solid information and not someone's opinion on leaving a small amount of DEF in the tank when truck is stored for the winter in freezing temps. I already know when DEF freezes and gets thawed out it's fine, no harm no foul. What my concern is whether it could harm the DEF pump, ie... corrosion, cracking, locking up over the stored period ? I might have a gallon give or take still left in the tank and not worried about the tank itself because the little that's still in it could expand when froze slightly and still be ok, but more for the pumps safety. Being that it's mounted on top of the tank may help but unless it gravity drains down there is still fluid in the pump. Thanks
 

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The freezing temperature of DEF is 12F, so if you don't expect temperatures that low, I wouldn't worry about it.
I'm not sure if urea changes the freezing characteristics such as propylene glycol does where it turns to slush as opposed to an expanding solid like pure water does.
 

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Hello Klhansen, thank you for the post but apparently you did not read and comprehend my post.
I do appreciate it tho. Merry Christmas
 

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You're correct in that I didn't comprehend. I took your post as you knew that DEF would be OK if frozen and rethawed, not necessarily that you knew the actual freezing temp. Sorry for the misinterpretation.
I know that there are tons of trucks that are up on the north slope of Alaska and in Fairbanks that are outside in way below zero temps, so I would suspect that the pump is not damaged by freezing.
 

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Hello fellow truckers, looking for solid information and not someone's opinion on leaving a small amount of DEF in the tank when truck is stored for the winter in freezing temps. I already know when DEF freezes and gets thawed out it's fine, no harm no foul. What my concern is whether it could harm the DEF pump, ie... corrosion, cracking, locking up over the stored period ? I might have a gallon give or take still left in the tank and not worried about the tank itself because the little that's still in it could expand when froze slightly and still be ok, but more for the pumps safety. Being that it's mounted on top of the tank may help but unless it gravity drains down there is still fluid in the pump. Thanks
You should have no worries regarding the SCR system and your DEF pump and lines. They system has a purge function which empties the system thus preventing damage to the lines and the pump should it freeze. If I am not mistaken this function is common to all SCR systems. Also, the system is constructed with materials that are compatible with DEF so no corrosion and the pump is a diaphragm type pump with nothing that would lock up. The following is the workshop manual description of the function: (reductant = DEF)

When the vehicle is shut down, the PCM closes the injector and actuates the reductant purge valve, causing the pump to reverse flow and bleed down pressure on the reductant pressure line. The PCM then opens the injector to allow gas to enter the reductant pressure line, which in turn allows the pump to purge all remaining DEF from the system and return it to the reductant tank. The PCM closes the injector and returns the purge valve to the forward position.
 

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Discussion Starter #6
Thank you for the reply with good information. Thinking about it more after I asked, I concluded that there are many other DEF system vehicles out there and some in more severe conditions than I've described and then realized I hadn't heard of this being any big problem. I'm still relieved non the less. lol Thank you
 

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Yup. The manufacturers pretty much figured it all out.
 

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You should have no worries regarding the SCR system and your DEF pump and lines. They system has a purge function which empties the system thus preventing damage to the lines and the pump should it freeze. If I am not mistaken this function is common to all SCR systems. Also, the system is constructed with materials that are compatible with DEF so no corrosion and the pump is a diaphragm type pump with nothing that would lock up. The following is the workshop manual description of the function: (reductant = DEF)

When the vehicle is shut down, the PCM closes the injector and actuates the reductant purge valve, causing the pump to reverse flow and bleed down pressure on the reductant pressure line. The PCM then opens the injector to allow gas to enter the reductant pressure line, which in turn allows the pump to purge all remaining DEF from the system and return it to the reductant tank. The PCM closes the injector and returns the purge valve to the forward position.
Wow... that is amazing.

Ford Doctor, you post some of the coolest stuff.
 
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