DEF Head Failure

[howie1234]

I have been reading on different sites about the DEF head failing and having to be replaced.  Does anyone know if there is a recall?

[wolfe10]

You will need to give us more detail:  Make of engine, engine family and SN.

[hermanmullins]

Jerry,

I have little to no experience with DEF, however I have a friend that runs a very large truck shop and Roy said that he change the DEF pump on 4 to 5 engines a month. But to be honest, I wouldn't know one if it were in front of me. Joe L. will have a better handle on your question.

Herman 

[jleamont]

Howie, very common on Freightliner products from the big trucks down to the Sprinters. The Def Header is the DEF tank sump, filter and potentiometer unit (for the gauge if equipped) (no pump, that sits on top of the tank). No recalls that I am aware of.

The biggest issue we see in the North East is if you fill the DEF tank in the winter and park it for an extended period of time (overnight), since DEF freezes, by poor tank design (Freightliner tanks) there is no room for the DEF to expand as it freezes and it cracks the plastic header within the tank. We have a policy at work DO NOT FILL THE DEF AT THE END OF THE DAY, FUEL TANKS ONLY. We change them by the dozens as a result of that and what we have become a custom to "routine failures for no reason".

When the engine cannot see the DEF tank level it will send the engine into derate (power reduction), I have had them just shut an engine off at highway speeds already also if it was damaged and shorted internally. The trucks have an "ENG FAULT OVRD" switch (that's how its labeled), you can press the button on the dash while cranking the engine and it will restart to limp it somewhere, I believe it will give you 4 hours at that point.

[manholt]

Even on mine, it say's, "DO NOT FILL TO TOP!"  Mine is 15 gal.  We put in 10 gal the other day & put a red tape on it.  4 boxes of 2.5 gal each.  The tank also has a red tape for low point.

[jleamont]

27 minutes ago, manholt said:

The tank also has a red tape for low point.

Do you not have a gauge on the dash to monitor the level?

[campcop]

Tiffin had a problem with Def head sensors with their 2017-2018 models. The sensors were defective from their supplier. The sensors would give a false reading and cause a MIL light and then a derate of the engine. Most failed by 20,000 miles. Ours just failed at 19,000 miles. I changed out the head myself. Tiffin shipped me the new part over night. On ours, the whole tank had to be removed which was the hardest part of the repair. Had to drain 10 gallons of def first.

[kickaha]

So, is there an additive one can add to the DEF to keep it from freezing? Seems  to me that since DEF is required by the feds, someone would have developed a product like this already.

[jleamont]

On 9/26/2020 at 10:31 AM, kickaha said:

So, is there an additive one can add to the DEF to keep it from freezing? Seems  to me that since DEF is required by the feds, someone would have developed a product like this already.

No, the system is designed to freeze. When you shut the engine down the DEF pump runs in reverse to purge all def from the lines and pump back to the tank. This is why it’s critical not to top it off for winter storage. The Freighliner tank has a defect in its design, the cap is placed too high on the tank which allows the user to top it off and creating a lack of space for freeze expansion.

Edited September 28, 2020 by jleamont

[wayne77590]

How many gallons in the FL DEF tank - 2015 Winnebago Tour?

I watch my guage and when I have one or two bars left - depends on how far I have driven - I'll put in a couple gallons or so.