Man I’m tired of these rotten DEF systems

[J&JD]

Beautiful 4 day stop at a really nice new rv park in Northern California. All packed up, everything secured for the trip home. Fire up the Cummins and damn if it doesn’t throw a check engine light and a message saying “low DEF”. My dash gauge shows 2 bars in the tank and I know there’s at least 1/2 tank as I had just visually checked it. Drove about 40 miles and stopped at a truck stop and filled the 13 gallon DEF with 7.5 gallons of truck stop DEF. Obviously I wasn’t low on DEF.
Drove about 20 miles with the check light on and all of a sudden the light goes out and the DEF gauge is back up to full (4 bars).
I’m on my second DEF sensor and now I’m worried that this one is going bad after just 20k miles. This is just stupid, poor engineering that should never happen with a system as expensive as this one.

 

[Joe Hogan]

In my opinion this DEF System is a wacky lab fix that escaped before or even ever ready for commercial applications.
Government dictates driving bad systems.
Early catalytic converters suffered similar problems that were finally fixed with widespread adoption of electronic fuel injection.

 

[Rich W.]

I think you would benefit from carrying a DSS with you because eventually this could lead to derate and all the fun that comes with it. You’ve probably seen this many times before but here it is again anyway: DEF Sensor Simulator

 

[Rich W.]

In my opinion this DEF System is a wacky lab fix that escaped before or even ever ready for commercial applications.
Government dictates driving bad systems.
Early catalytic converters suffered similar problems that were finally fixed with widespread adoption of electronic fuel injection.

Yeah Joe you’re right - this was forced on the public long before the engineering was sufficient to develop reliable systems. And to illustrate that point, they had to exempt emergency vehicles and because it was considered an “undue hardship”, agricultural equipment as well. I’ve always said that it is also an undue hardship to have your home on wheels leave you stranded by this equipment but apparently we don’t have a loud enough voice. Fortunately around 12 years after the mandate they finally appear to have developed a reliable system; time will tell.

 

[J&JD]

I think you would benefit from carrying a DSS with you because eventually this could lead to derate and all the fun that comes with it. You’ve probably seen this many times before but here it is again anyway: DEF Sensor Simulator

I do carry a simulator. I was/am hoping that I will not have to utilize it. Still doesn’t give me much piece of mind concerning this sad system.

I also carry a new DEF head. Has anyone tried to replace the head themselves? Can it be done without removing the tank on a DS 4018?

 

[Jim]

I do carry a simulator. I was/am hoping that I will not have to utilize it. Still doesn’t give me much piece of mind concerning this sad system.

I also carry a new DEF head. Has anyone tried to replace the head themselves? Can it be done without removing the tank on a DS 4018?

I considered it on my London Aire, and then quickly reconsidered it. Not a job I would want to take on.

 

[Neal]

@J&JD any updates on your situation?

 

[J&JD]

@J&JD any updates on your situation?

No real updates. I’ve been waiting on a back ordered DEF filter before I replace the fluid in the tank with fresh DEF. We have a short trip (80 miles) planned for the 19th hopefully there will not be any warning lights. I have mounted my def head simulator in the compartment so I’m ready just in case. I’m also considering installing a ball valve on the tank heater hose. Thanks for asking.

 

[CaptainGizmo]

I do carry a simulator. I was/am hoping that I will not have to utilize it. Still doesn’t give me much piece of mind concerning this sad system.

I also carry a new DEF head. Has anyone tried to replace the head themselves? Can it be done without removing the tank on a DS 4018?

FWIW, I watched as the road mechanic replaced the DEF head on our '19 4369. Took him all of maybe 15 minutes of actual work time. He was able to access everything needed from the top without removing anything. Clamped the lines, and swapped heads.

It's sickening how many of these things fail...and the newers never seem to hold up; despite the manufacture saying "oh..this is the Gen x and it's better now." They said that way back on Gen 4 and now I think they're on like Gen 8. Geesh.

 

[J&JD]

R&ring the head in my 17DS 4018 does not look like an easy job. No room to just pull the head out without dropping the tank and dropping the tank with all the connections looks pretty tough. Not sure I want to tackle the job.

 

[redbaron]

that one bolt in the middle of the tank is the strapping that holds tank in place. Once that is removed and the zip ties are cut, you have plenty of room to lift it and rotate it for angles to pull the head out. looks worse than it really is. The first time is about a 30 min job, but after that it would take you 15 min tops to do it.

You mentioned getting a filter, thats a good plan. I would drain and replace the filter and fill with fresh once you are done with everything.

 

[J&JD]

An update on my DEF head problems. New head installed along with a shut off valve for the tank heater line. I now believe that the tank heater was the main cause of my sensor problems as you could feel how hot the lines were after a short trip with the weather around 60 degrees outside. No way should there be engine coolant circulating through the system. Maybe the third time is the charm as this is my 3rd DEF head.

 

[Jim]

An update on my DEF head problems. New head installed along with a shut off valve for the tank heater line. I now believe that the tank heater was the main cause of my sensor problems as you could feel how hot the lines were after a short trip with the weather around 60 degrees outside. No way should there be engine coolant circulating through the system. Maybe the third time is the charm as this is my 3rd DEF head. View attachment 26619

Did you install the shut off valve on the tank heater line as a backup?

 

[J&JD]

Did you install the shut off valve on the tank heater line as a backup?

Where we live here in Northern California it rarely if ever freezes and we don’t participate in @neal’s snow caravans so I believe I will just leave the valve shut until or unless those on the rv forums advise me otherwise. From what I understand, the factory valve is only supposed to activate open when the DEF tank gets somewhere in the neighborhood of 11-12 degrees. Never in my 20 plus years of pusher ownership have I ever come close to being around that temperature range.

 

[Jim]

Where we live here in Northern California it rarely if ever freezes and we don’t participate in @neal’s snow caravans so I believe I will just leave the valve shut until or unless those on the rv forums advise me otherwise. From what I understand, the factory valve is only supposed to activate open when the DEF tank gets somewhere in the neighborhood of 11-12 degrees. Never in my 20 plus years of pusher ownership have I ever come close to being around that temperature range.

Yep, that should work.

You might want to leave it open and let the DEF header operate normally, and then upon failure you could use the valve. That way you would have an emergency "get out of jail card" to use until you can find a 4th replacement header.

But either way, I'd say your ahead of the game!

 

[J&JD]

Yep, that should work.

You might want to leave it open and let the DEF header operate normally, and then upon failure you could use the valve. That way you would have an emergency "get out of jail card" to use until you can find a 4th replacement header.

But either way, I'd say your ahead of the game!

It’s not the DEF head that is acting abnormally it’s the valve that controls the engine coolant circulating through the head. When it fails it fails open which can then cause the head sensors to fail and then all hell breaks loose with engine warnings etc. if I don’t need heat circulating through the head why even chance it. I’ll leave the valve closed for now.

 

[redbaron]

It’s not the DEF head that is acting abnormally it’s the valve that controls the engine coolant circulating through the head. When it fails it fails open which can then cause the head sensors to fail and then all hell breaks loose with engine warnings etc. if I don’t need heat circulating through the head why even chance it. I’ll leave the valve closed for now.

I’ve kept mine closed since installing.

 

[Jim]

I’ve kept mine closed since installing.

Then why bother replacing the DEF header? Just put in the valve and call it good. Same end result.

 

[J&JD]

Then why bother replacing the DEF header? Just put in the valve and call it good. Same end result.

No, because the head was damaged and just putting in a valve would not cure all the codes the damaged head was throwing. The new shut off valve will , hopefully, stop a bad coolant circulating unit from damaging the new DEF head.

 

[Jim]

No, because the head was damaged and just putting in a valve would not cure all the codes the damaged head was throwing. The new shut off valve will , hopefully, stop a bad coolant circulating unit from damaging the new DEF head.

I think the damaged head only throws codes when the DEF overheats. A few cycles of not overheating and the code will reset.

If that is the case, and it certainly was the case with mine, then bypassing the DEF header altogether, which happens when you terminate the flow of coolant into the DEF header, will allow the required cycles to occur and the code to go away.

Or am I missing something?