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I see a lot of people jumping to DEF here... but has anyone considered what the fluid is? Especially considering it just started over a year after deleted.

Does it smell like oil? ATF? DEF? Fuel? My truck spins ATF from the transfer case out of the yoke seal, it gets on the underbody and frame in that area. it takes a long time to get to "drip" levels. Its anti rust IMO ROFL. Although TBH that doesn't look like its coming form the shafts. Almost looks like its coming down the frame form the engine area.
 

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I see a lot of people jumping to DEF here... but has anyone considered what the fluid is? Especially considering it just started over a year after deleted.

Does it smell like oil? ATF? DEF? Fuel? My truck spins ATF from the transfer case out of the yoke seal, it gets on the underbody and frame in that area. it takes a long time to get to "drip" levels. Its anti rust IMO ROFL. Although TBH that doesn't look like its coming form the shafts. Almost looks like its coming down the frame form the engine area.
Definitely appreciate your input as obviously people can miss stuff when jumping to conclusions, but that's 100% crystalized DEF fluid. When these shops 'relieve' these trucks from their emissions systems they disconnected the injector and tie up the def line to the frame rail exactly where that picture is. You can look at your own truck but that location is exactly where the start of the SCR begins and the injector is located. Def will auto siphon out for days/weeks/months depending on how much fluid was in there and just when you think it's done, you go through an elevation change or a temperature swing and more appears.

I just dealt with this a month ago and it crystalizes just like that, in that exact same location. It's DEFinitely DEF ;). To the op, do your self a favor and hose that down so it doesn't corrode anything.
 

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no DEF on my truck.. I didn't know that about the crystalized stuff. crazy!

Thats weird that it just started leaking a year later.. would you want to drain the tank anyway if it wasn't being use? makes sense about disconnecting the pump.

It's DEFinitely DEF ;)
you couldn't help yourself could you ROFLMAO
 

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no DEF on my truck.. I didn't know that about the crystalized stuff. crazy!

Thats weird that it just started leaking a year later.. would you want to drain the tank anyway if it wasn't being use? makes sense about disconnecting the pump.


you couldn't help yourself could you ROFLMAO
The pump should be turned off in the programming so it "shouldn't" so long as it was done correctly. Shouldn't be necessary to unplug it but it's not a bad idea.

Some people drain it, others don't. I'm assuming it started leaking again because the right combination of temperature and pressure turned the crystallized def back into a liquid momentarily. I'd have to look at a phase diagram to confirm but that checks out in my head. Draining it is relatively easy though. you can disconnect the fill tube right at the tank. It's at the rear passenger side of the tank which is located on the drivers side pretty close to the fuel door. Then just get a little hose and a siphon pump and a 5 gallon def tank to drain it into. You might need two depending on how full it is. Personally I did this then filled with distilled water, drained, filled, drained after dealing with this **** making a mess on my driveway and my friends driveway. It would randomly start/stop.

But yeah it crystalizes when exposed to oxygen. It's nasty stuff. Fortunately you don't have to get it near your hands all that often.
 

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Discussion Starter · #25 ·
Yes I knew it was def based on the crystallization. But I myself found it odd that it started draining after all this time especially haven taken this route before without issue. Perhaps I didn’t notice it before? Only thing different about this trip as kaleog mentioned is just the right temp at the right elevation. Drove up in in the heavy tow tune(usually use light tow tune no-travel trailer is around 8.5k lbs) in 5th gear almost whole way as it was almost 100F outside and didn’t want truck to overheat going up and down mountains so I just kept it in one gear. I let the truck do it’s own thing on the way home and so far the def has stopped leaking. Truck will tow in 6th and pretty much ride the turbo up the hills if I let it. Gauge still reads full so hopefully the tune is doing right by me. Based on the puddles it left over the course of the week there is no way it’s still full. That being said I want to thank everyone for their help. I was in a bit of a panic when I first noticed it! A little unsettling being hundreds of miles from home and not knowing if your towing rig will get you home. But all is well and made it home in no problem.
 
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