It is Minus 30 degrees here in Stanley Idaho. My truck sits outside. I have the Block Heater plugged in but worry about my DEF tank being frozen. It's a 2012 6.7 Liter. How does the DEF Tank Heater work?

 

From the service manual for my 20, there are two heaters, one in the line and one in the pump.

 

Jollyrogr, thanks for that post. That explains to me why the GPCM was the culprit when mine threw reductant heater codes and will help should that problem arise in the future.

 

Wow that was a Lengthy explanation. I hope that means that when the Ambient Temperature are in the Minus 20 to Minus 30 F or more range the heaters will keep the DEF from being frozen?!?!?!
While I have the Block Heater Plugged in and on.. I don't see how the DEF heaters would be on when the Truck is Not running???

Thanks,
GARY

 

The DEF heaters are only on when the truck is running. That's why the pump empties the line and injector when the truck shuts off.

 

Is this accurate? I've never heard of this line emptying on shutdown. All years 6.7 do this?

 

OP wants to know how the DEF is prevented from freezing when truck is turned off. It is not. The fluid can freeze solid depending on temp. The truck can run for up to (I believe) 30 minutes after a cold start without throwing a code while the reluctant heater assembly thaws enough fluid for injection. The system is not designed to liquefy the entire contents of the tank (although it might). There is supposed to be an air gap at the top of the tank after filling to allow for freeze expansion. You used to get a special fill hose when you bought def from from ford now you have to guess. There is a nice write up at the end of the 6.7 coffee table book on the system. Block heater has nothing to do with this system.

 

It freeze solid, The heaters to thaw it are in the tank and line to the injector.
That's why it's important to NOT OVERFILL the tank. If you have DEF in the FILL Tube, It can freeze and break.
The Motorcraft DEF had a special fill tube that would stop flowing when the tank level hit the tube's breather tube preventing over fill.
I fill mine in November and then I'm carefull during the winter months to not "Top Off" the tank. Always leaving it just short of full.

 

That info was copied and pasted from the service manual for 2020.

 

I appreciate the replies. It warmed to 20 above zero F today so I started the Truck and let it warm up. Likely my DEF Tank is mostly froze with the many nights below minus 20 F. It did throw code and will read it soon....

I am in hopes all will be fine when the tank THAWS.

Gary

 

According to this site, it freezes at around 12 degrees...

From that website,

• A full DEF tank is less susceptible to freezing than a tank low on fluid. Keep the DEF tank above 50% full during winter to allow less room for ice crystal formation. The smaller capacity minimizes exposure to freezing air temps. Topping off the tank regularly prevents freeze-ups.

It's been awhile since I filled mine, I'm going to check the dash gauge and see if it's under half a tank...

 

bottom line, nothing to worry about out. As Jon mentioned don't overfill. Everything else takes care of itself.

 

Apparently so.....

When I shut down my 2015, you can hear the DEF pump running for about 10 seconds

 

Am dealing with the joys of a frozen fill tube now on my 2025 F450 with a service body. The DEF fill tube comes out between the cab and the service body and is exposed to the elements.

We had several weeks of -35/50F just before Christmas (3rd coldest span ever up here) and I noticed my DEF % going down very rapidly - from 35% to 9% in the span of 1.5 days (lots of engine idle over that time, but few miles on it - less than 200mi). After fixing a frozen cell site (tarps and herman nelson's are awesome), I went to go fill my DEF and found that my fill tube had froze (got DEF all over me, side of the truck and the ground). I parked it, switched trucks (work vehicles) and went home for the holidays. Today (warmed up to -15F) I went to deal with the frozen DEF and found the fill tube a block of frozen DEF. I wish I'd thought about putting the herman nelson to it while we had it out before Christmas. I have it in the heated shop at work with a heater pointed at the fill tube... that will solve this issue... but I'm not sure how to prevent this from happening in the future.

There shouldn't have been any DEF to freeze initially given that my tank was under 50%. I get why it's frozen now... but due to having a service body with that fill tube exposed to the elements (I had to take a torch to the cap just to melt the frozen ice (snow and road dirt) off the fill cap), I'm not sure how to prevent this from happening again... ? This is also my first diesel truck.

Edit.#1
I stopped off at the shop we use and chatted with a mechanic there about this when I went to gas up my borrowed work truck. What he figures is the last time I filled the DEF, I probably filled it right to the top (which thinking back about it, is likely). Some of that froze somewhere in the fill tube since our normal winter is well below -12 on average. Since the truck doesn't normally go indoors at any time, it's been frozen ever since and I only noticed it when I went to fill it the last time. It seems to be thawed now... so will go get a jug of DEF and see if it takes a good % of it. If not, will leave it in the heated shop overnight and deal with it tomorrow... but I'd rather take it home. Its always nicer to drive "your" vehicle rather than borrowed ones.

Edit #2.
Seems like I spoke too soon... still frozen. The top part of the line thawed, but it won't take any DEF... so still something frozen in there. Will leave it in the shop overnight and try again tomorrow. The good news, is this is a good learning lesson. Don't overfill the DEF in the winter time, because this is a PITA and had this happened in a remote work place (where I frequently travel) this would have been a major issue.

 

Hopefully that fill tube slopes towards the tank the whole way. There's a possibility you have crystallized DEF in a low point. It should dissolve with fresh DEF on it.