Heated DEF reservoir

[SCOTTY088]

Looking for insight on the heated DEF reservoir. Does it heat only when vehicle is running? Does it utilize battery power when vehicle is not running? All the manual says is that it is heated and not to overfill or freeze damage may result. Just curious about my truck sitting out on below zero nights. Any info would be greatly appreciated.
Scotty

 

[wyosteve]

My understanding is that it is heated only when running. The caution not to overfill is due to the heater being in the reservoir and not the fill neck, so if the neck freezes, it wouldn't thaw.

 

[sag2]

It is correct that it only heats when the engine is running, and it takes quite a while for it to thaw depending on the ambient. DEF injection is suspended until it heats enough to inject.

 

[SCOTTY088]

My concerns stem from truck sitting in minus degree temps for several days.

 

[DonFitzwater]

"My concerns stem from truck sitting in minus degree temps for several days."

Don't be concerned. Nothing is going to happen to it. My truck will go months outside in waaaaaaay below zero temps and not have problems with DEF system.

 

[Hoefler]

As mentioned, DO NOT overfill it. Not only will it freeze in the neck, it will stay frozen if not given warm enough temps to thaw. Which means you can not refill it when needed.

 

[marathon]

As mentioned, DO NOT overfill it. Not only will it freeze in the neck, it will stay frozen if not given warm enough temps to thaw. Which means you can not refill it when needed.

Part of the problem with a full tank in cold weather is that the DEF is ~32% urea and the rest is good old water. There isn't any room for ice expansion when the tank is full and it will burst. Repacing the plastic system would be an expensive job. I think the freezing point is 12F.

 

[DonFitzwater]

"There isn't any room for ice expansion when the tank is full and it will burst."

This is NOT true. I've had mine completely full on two different trucks and exposed to sub-zero temps for days. No damage. The tanks are well designed and can handle it.

 

[marathon]

My manual says to be careful not to over fill because if the DEF freezes the tank could be damaged.

 

[SCOTTY088]

When my DEF tank gets down to around 1/2 I have the wife watch the gauge as I slowly fill the res. and stop at just about at the full mark. That seems to work well. I have read all the posts on letting the reservoir get too low and when refilled get the dreaded DEF see dealer. Knock on wood 44k with no major problems.

 

[JR]

Ice is a bad mama! This is what happened when operations forgot to drain exchangers out at First Energy. Those are (32) B7 grade 3/4" studs that fastened the blinds. Didn't stand a chance.

 

[Newsa]

The red tank appears to be made of a composite material that can expand when the def freezes.

If the def freezes in a metal tank, it will likely bust the tank even if it is not full.