Frozen DEF

3930dave · Jan 8, 2018

I'm scratching my head over this one....

Heard a few guys talking about late model pickups here with frozen DEF tanks, and no Fault Codes.

I know of vehicles (Cruze for example, also some TDi's.....) that have had the DEF tank heaters fail, but usually throw codes when that happens.

So assuming these pickups had working DEF heaters, then what are you supposed to do when the temperature starts heading to -40 ?

Other than leaving the truck running all night, or parking in heated garage, what other options are there ?

Rgds, D.

k0ua · Jan 8, 2018

3930dave said:
I'm scratching my head over this one....

Heard a few guys talking about late model pickups here with frozen DEF tanks, and no Fault Codes.

I know of vehicles (Cruze for example, also some TDi's.....) that have had the DEF tank heaters fail, but usually throw codes when that happens.

So assuming these pickups had working DEF heaters, then what are you supposed to do when the temperature starts heading to -40 ?

Other than leaving the truck running all night, or parking in heated garage, what other options are there ?

Rgds, D.

I have thought about that myself, and sure don't have any answers. The whole DEF thing looks like trouble waiting to happen. Especially in cold climates.

4570Man · Jan 9, 2018

It freezes at 12 degrees Fahrenheit according to google. That sounds like a terribly thought out plan. I guess if parking inside isn’t an option you’d have no choice except to add a heater. It’s a good thing my 1992 Chevy doesn’t have any DEF to freeze.

3930dave · Jan 9, 2018

4570Man said:
It freezes at 12 degrees Fahrenheit according to google. That sounds like a terribly thought out plan. I guess if parking inside isn’t an option you’d have no choice except to add a heater. It’s a good thing my 1992 Chevy doesn’t have any DEF to freeze.

AFAIK, anything sold here will have heaters built into the DEF tank. Youtube has examples of people replacing them on Cruze's - PITA to deal with, but at least certain of those years don't require dropping the tank. Some thought went into servicing a "Replace within ...... miles, or total shutdown will happen" item.

All that ^ aside, I've always wondered - What happens when the vehicle sits through an extended (Canadian) cold snap ? If the DEF tank heaters are any kind of wattage at all, they'll flatten the battery quickly.

Battery charger + re-programmed DEF heater controller ?

Rgds, D.

LouNY · Jan 9, 2018

I have wondered about DEF freezing and giving problems; it got downight cold this last week and my pickup is a RAM 1500 with the little diesel when I filled up last week I made sure to give it a heavy dose of power serve for the fuel. I worried about the def and what it might do or cause as most of my driving is short trips now days, I do let it idle a lot. So far I haven't received any def messages or had any def related issues. I'm pretty sure the def heater only runs with the truck running as it is electric and with the weather being below zero F for a week it should have stressed it if it was going to. This is my third winter with this pickup and no def issues so far, knock on wood, its been doing a decent job for me.

3930dave · Jan 9, 2018

LouNY said:
I'm pretty sure the def heater only runs with the truck running.....

Agreed; I left that background thought out of my post.

The only thing I can see working reliably is having a DEF drainback system in place so lines don't freeze - if the tank is frozen, then the heaters will need to do their thing for a while to thaw the DEF before it will flow. That takes time though, which may not pass EPA requirements (?).

Rgds, D.

number two · Jan 9, 2018

DEF is used to reduce the NOx from high combustion temps.

The Nitrogen and Hydrogen from the DEF combine/convert NOx into Nitrogen gas(our atmosphere)and H2O-water vapor.

Since high combustion temps won't happen for some time when very cold,this allows the DEF tank and line heaters time to warm the DEF so it will be ready when needed.

k0ua · Jan 9, 2018

number two said:
DEF is used to reduce the NOx from high combustion temps.

The Nitrogen and Hydrogen from the DEF combine/convert NOx into Nitrogen gas(our atmosphere)and H2O-water vapor.

Since high combustion temps won't happen for some time when very cold,this allows the DEF tank and line heaters time to warm the DEF so it will be ready when needed.

So are we saying the fact the DEF may be frozen while in the tank in very cold weather, is not problem, and it won't hurt anything, the heaters will just thaw it out and it will be ready when it is needed then?

David_Kb7uns · Jan 9, 2018

number two said:
DEF is used to reduce the NOx from high combustion temps.

The Nitrogen and Hydrogen from the DEF combine/convert NOx into Nitrogen gas(our atmosphere)and H2O-water vapor.

Since high combustion temps won't happen for some time when very cold,this allows the DEF tank and line heaters time to warm the DEF so it will be ready when needed.

Think I remember reading that some place that it would hold back on errors until it got thawed out. No NOx until it gets warmed up anyway.

I will stick with the 5.9 Cummins for right now do not need any rocket science. Just lucky the 2 tractors RTV and mower are Tier 3 .

David