Can def go bad in three months over the winter?

[Nutfarmer]

it was egr cooler. I don’t see that that would have anything to do with the def system. There are now shop manuals on line. I think I payed 50 dollars for the last one I downloaded. Paper manuals seem to run about a hundred dollars per inch in thickness. With a years time and only 300 hours run time this is the second down time for the tractor throwing a code.

 

[Jake M]

Well, as I said, you may or may not like what I can come up with..... The fact that they manually checked it goes in their favor. There's a couple of ways of on board monitoring for DEF quality, and only one is (essentially) dead nutz reliable in terms of actually keeping track of the DEF. The drawback to that system is that they're a problematic sensor. Not problematic by 1980's sensor standards, but by modern standards... You can bank on changing one or three in the life of a machine. Other methods rely on indirect monitoring of the performance of the SCR system (the "def" system), and interpolating the DEF quality from that. Jumping on a DEF quality code from one of those is a rabbit hole. The refractometer is pretty much dead on, and NOT dependant on the machine.

My concern, and why I was asking about the EGR cooler is that those fail two ways. (Well, three, but if it was an external leak that wouldda been your original complaint). They either plug up (which means you ignored other stuff in the engine and fed it dirty oily sooty crap. Not common), or they leak internally. This inevitably sends small amounts of coolant through the combustion process, out the exhaust again, out through the DPF brick and the SCR brick (and any others they have in line on any given system). That will reduce the effectiveness of the SCR catalyst, and if the DEF quality monitor is based on performance, it'll flag for def quality. That troubleshooting step will have you follow up appropriately to validate the test, and repair literally everything related to the SCR system first. But going to the refractometer kind of validates that they didn't just let the new kid jump on it by a code description and without diagnosis. Did they by chance not the concentration the DEF was at?

 

[Nutfarmer]

Good information. The egr cooler was leaking internally. What I can’t figure out was when I opened the def tank it overflowed by at least a quart. How could it be over filled? They said the def was over concentrated. The biggest think now is to avoid it happening again.

 

[Jake M]

Something I missed in the last post- When I said that coolant messes with the recuction catalyst- It does that for sure, but it's doesn't "poision" the cat. It burns out in the natural processes of the whole entire assembly. that part of the issue is a self-correcting situation. Hope I didn't scare you with that. Other chemicals, fuel additives, etc- I'm not talking about that. Just coolant...

Def tank overflowed? Hmmm.... There's coolant in the DEF tank, to defrost it in the winter time. I'd bet you'd see if a quart was gone, or if you're not sure check it now, and you'll certainly get a result in a short time. Unless you have the green coolant. I'm pretty sure you'd have the gold coolant in that one, harder to see, but the green coolant would show up right off just by color. My vote is it was a mechanical thing that did that. The tech carried a loose tank to the bulk bin to fill it before installation (speculation only), and got it filled while it was tipped, so the air space filled. Or perhaps it was filled before the mounting hardware was tightened. Maybe something on the trailer got the air space in the tank all wierd? If it were me I'd keep an eye on the coolant for a bit, but I wouldn't loose much sleep over that just yet.

Overconcentrated kind of goes to extended storage, or unsealed storage, or generally evaporation. Can you smell DEF where it's stored and/or around the tractor when it's not in use? If so, the storage isn't adequate, or there's a vent not doing it's thing on the tractor tank. You said you have the same DEF in other machines- Are you topping them right up to the top every time you fuel up? If so, don't do that. My rule of thumb (which is not a rule, it's not science, it's just experience) is that if you're in a commercial truck for example, where it gets used a lot, don't fill the DEF until it's half full or less. In equipment where the use is sporatic or intermittant, let it go to at least a quarter, maybe lower. The stuff doesn't get used that fast, don't go pushing limits, but let it run down. Packing up for long term storage is different, Full or drained for that, but for intermittant use... Use enough that it keeps the whole tank fresher.

I'm not jumping on, but not ruling out that the DEF you got may have been at a higher percentage. It can happen before you get it. They're very good about going batshit crazy if they think the concentration is low ('cause "cheaters"....), but if it's high, they're pretty good about "getting by" for a tank or three before they get upset at you. So that's plausible as well.

Overall though, just make sure you're getting the DEF from a decent source. Totes from a busy parts store, where they're not all dusty on top of the box. Bulk at the filling station, but only if it's a genuine truck friendly place that actually keeps it moving. Smaller places are starting to show up with that, but dont' have the volume to move it very quickly.

Wherever you're sourcing DEF, don't sweat the brand. Most manufacturers (and I'm SURE John Deere as well) will either recommend a brand, or have a private label of their own, one way or another having a paper contract with somebody. DEF is a little unique in the automotive fluid world. Most all automotive fluids, including fuels, don't have a "recipe" for making them, they have performance specifications. The actual molecular and chemical makeup can very tremendously from one batch to the next, but so long as they meet the spec number, they get the job done. DEF is a chemical. No negotiations, no marketing wank for the sales department to get ahold of. (Note the lack of advertising for DEF....) No performance specs, because they're not needed. It's literally all the same. Kind of a little relief in among all of it's other blessings, you can't get a bad one unless it's a genuine coutnerfeit..... Aqueous urea, 32.5 percent, plus or minus some small amount, less than a percent up or down when it's new. 0.7 maybe but don't quote me on that. Get it where it's cheap (although maybe skip eBay and the dollar stores). Get the store brand over the blue brands, no worries. But mostly, the thing that gets you the most security, get it where they move a bunch of it so you know the inventory hasn't sat.

 

[Nutfarmer]

Thanks for the info