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DEF problems What is the DEF header and how its been improved.

Tags :  def  |  def-header  |  emissions  |  kubota-landing  | 


DEF problems What is the DEF header and how its been improved.

Neil from Messick's here to introduce you to this fairly problematic part. This is a DEF header, and this part is responsible for a lot of headaches in our shops throughout the last number of years. I'm going to show you here how a DEF header works, how the manufacturers have improved the construction of these things over the years. Hopefully we could take a little bit of education here today and prevent you from having trouble with your DEF equipped equipment. Now, while this thing looks pretty complicated, when you start breaking down its function there's actually a lot of simple parts here that you can understand within this one large assembly. This coil that comes down here through the yellow and the gray caps is a heating element.

You're going to have a pump and a heater up here that pumps warm fluid down through this coil in order to warm DEF fluid up. It can freeze in the wintertime when it gets cold, and so this is going to help heat the tank up to keep the fluid flowing freely. The other lines here are going to dip down into the tank itself. There's one line right here that comes up to the quality sensor, that we'll talk about later, a vent line here in the top, and then an intake line to pull the DEF up, and then out into your exhaust system. This plug here at the top is for the quality sensor. That's this box that sits on top of the assembly right here. It measures that the DEF has the right proportions of the different ureas and waters inside of it that help it work properly. This silver pin right here that runs right down through the middle, if I flip this upside down you'll see there's a float on here. That is the level indicator for the float in your tank. This one assembly right here performs all of these functions. The heating, the dipping, the monitoring of quality, the measuring is all done by the DEF header.


There's a couple of called failure modes here of where these things can start to cause problems in your machine. The first one is going to be when this quality sensor in measuring the quality of the DEF itself that's in the tank. If you don't run your machine very often and you're not cycling fresh DEF fluid through it all of the time, it is actually possible for DEF fluid to break down over time, and the quality of it to drop in a way that it doesn't work properly in your machine anymore. That will start throwing codes on your equipment. Now, we hear timeframes as little as 90 days that you're supposed to be cycling all the DEF through the tank, or at least trying to get fresh DEF back down in there again. In the real world, the dates for that can stretch out quite a bit longer than that. You want to keep in the back of your mind that this is a system in the machine that you need to be flushing fluid through frequently in order to keep it fresh.

The other place that you can really cause problems with this quality sensor, ruin the sensor itself, and, in fact, ruin much of the DEF system on your machine is if you manage to put diesel fuel into your DEF tank.If you fill from a regular fuel pump, your regular hand squeeze diesel fuel pump that has the larger end that comes out of it, that end will not fit into your DEF tank. You've got a blue cap on there, a smaller hole that's supposed to tell you not to put the green diesel fuel with the big spout into that hole. If you manage to do that, which we see fairly frequently unfortunately in rental situations where the operators aren't familiar with the machines, and they're trying to fill the thing up with fuel, and they see a hole, and they pump it up, that diesel fuel can come and it will ruin this DEF sensor even with small amounts of diesel fuel.  It can go a lot further than that though. The plastics in the hoses that are used in order to handle the DEF, the urea that's in your DEF tank, none of them respond well from diesel fuel. The sensor is just the tip of the iceberg.

When we get into a system like this that's had diesel fuel put into it, we're often flushing tanks, sometimes replacing them, flushing and removing the rubber lines that go through up to the rest of the machine's exhaust system in order to get that diesel fuel out. It can ruin the whole system very quickly. That's why you see more and more of these now come through with covers over top of the DEF tank that makes it very, very obvious that you shouldn't be putting diesel in there.

How things have changed

Now, there's a positive spin to this story. There's a lot of innovation and iterations of these parts here that have happened over the last several years where a lot of the problems that we would have experienced with this thing have started to be fixed. There's a couple of different ways that the companies have gone through and addressed and improved these parts. Now, I should be clear that this isn't a Kubota problem. I was talking beside an SVL95 here earlier. Every machine that's going to have a DEF system on it is going to have these functions. By and large, many of these companies are probably using very similar parts or even parts from the same suppliers. Because a lot of this stuff comes out of automotive industry suppliers a lot of the time. 

There's early failure points that we saw on these that have now been fixed. Right up here on the very top is this little box, and that's where the actual DEF quality sensor is. There's an electronic circuit board that's inside of this. Early on what was happening is that ammonia gas was getting up through the inside of this thing, up into the top of this. That ammonia gas was corroding the circuit boards, and then these quality sensors would stop functioning.  Now, as we've learned a little bit more about that, they've changed the way that they seal these things up now. That ammonia gas can't get from the tank up into the sensor as easily. The potting, the plastic material that sits over top of those electronic boards has been changed now to tolerate that ammonia much better. 

We haven't seen a failure of a DEF sensor at all in this last iteration of this part. It has been perfect so far. The potting is different. Then another change that was made as well was a software change to your equipment. This is what your DEF tank looks like. I am not an artist. You've got a tank with this guy that comes down inside of it. Now, previously we did an update here to the computer software that runs on your machine, and it used to be that you'd have a level sensor down in here. Then when the level of that DEF would get low, it will turn on a light on your dash telling you that the tank needs to be filled. Now, the issue with the ammonia is that the more surface area that you've got for DEF to splash around this tank, the more of it can evaporate off and turn to ammonia inside the tank. A software update was done so that the level for your tank now reads differently.

Previously where that light, that fill light would have turned on when the level was good and low, the fill light is now closer to up here. That causes people confusion sometimes because you can go just fill your tank up with DEF, go out and run for a little while, and, what the world, this light is turning on telling me to fill it up already. Again, this is the reason for it. It's trying to reduce the amount of surface area that's available. By moving the fill line this much further up on the tank, all the DEF that would be splashed up on the sides, and stuff, of your tank, now stays covered. You don't have as much surface area up here for that ammonia to off-gas inside the tank. Ultimately you've got less of that ammonia collecting up here at the top of the tank and being able to impact those sensors. The ammonia issue was addressed in those two ways. One in software by moving this level up. One in potting this a little bit differently. That's how we get now working reliable DEF quality sensors. 

Tier 4 technology rolled out in 2008, and despite being around for 15 years now, there remains quite a lot of confusion around what is allowed to come out of that tailpipe. The government has different regulations for what is allowed to come out in different horsepower classes. Most of the equipment that you see around me here is under 75 horsepower and does not require DEF fluid. It's not treating those nitrous oxides that come out of the tailpipe that that DEF fluid is addressing. You will not find a DEF header like I'm showing here on any equipment under 75 horsepower.

Over 75 horsepower, you're going to need DEF fluid on your engine, and you're going to have some kind of DEF header assembly. That is irregardless of the manufacturer's equipment that you're looking at. Your on-road trucks, your heavy-duty off-road, whatever, is all going to use DEF fluid. Now, between 75 and 25 horsepower, and change, there's some decimal places in here, because these numbers are actually measured in kilowatts, you're going to need to treat soot. You're going to find a diesel particulate filter, or a DOC, a diesel oxidation catalyst, one of those two technologies on every diesel engine between 25 and 75 horsepower. Machines like this B-series tractor right here that come in under that 25 horsepower mark are able to meet emissions requirements with no external stuff on the outside of the engine. Traditional engine tuned in a way that it's meeting the requirements for soot and output.

It's a little bit more lax on the smaller engines than it is on the bigger ones. Still Tier 4 compliant. Don't let anybody tell you that an engine doesn't have emissions requirements. That's not the case. They all do, but the emissions requirements are more lax the smaller that the engine is. This is where the value of good dealer support and buying your equipment from manufacturers who stand behind their product becomes really important. We've seen four iterations now on this part getting it right, and I can now stand here on video and tell you that we have yet to see one of these things fail. They've been wildly more reliable than any DEF system that we've seen in the past. We have gone back now and updated every machine that's had these old failing parts on them with this new version. That's the value of good dealer support. When we're coming out, we're updating equipment, where our manufacturers are spending the money in order to go through reengineer these parts, install new ones on your equipment.

Makes us proud to be able to sell good stuff from good companies that support their product. From me talking to our service department here today, none of my service managers can remember any of our customers getting a bill to replace one of these things, for anything but maybe travel time, while our guys were on the road. That's not covered by warranty. Companies have stood up and taken care of these things and made them right. I'm proud to be able to support a whole bunch of companies that do that.

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