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Discussion Starter · #1 ·
Have a 2012 S77 combine here throwing error code: 521008/ 1

SCR system error: DEF pressure build up failure.

Agco has suggested it could be the DEF pump or the head unit on the DEF tank itself. Tried switching pumps between our two combines and error code still trips so we think the pump is ok.

Have a new control/ head unit that goes on top of and into the def tank to install and try next. Guess the tube that holds def can crack due to freezing, thus causing air leak and pressure problems.

Tried removing the old one and find it is quite hard to turn and get out of tank. Seems like we can only turn the head unit an 1/8 th of a turn or less counter clockwise, then try to pull up. Lots of resistance pulling it up and don't want to wreck the tank.

Anyone else removed one of these before? Should be an easy swap but I don't want to wreck something else in the process.

Cheers,

Steve
 

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We had that code also. Need to shine a light in and see if you have any dirt in the bottom of the def tank. Ours did as the stock vent is a bad system of getting dirt in there. Take the fitting off the end of the vent hose and see if any dirt is stuck to the inside of the hose. We had to drain and flush the tank to get all the little sediment out as it would float up and plug the suction screen and we also had to replace the pump. They can plug in the computer to check to see if the pump has any pressure also. We haven't messed with the head unit on the tank yet.
 

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Yes, clean the tank. We had a tractor that did the same thing and it was dirt in the DEF tank. Pull it, wash it thoroughly and it should fix it. The DEF crystallized over winter and left the residue that gets stirred up and clogs the filter.
 

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the filter will be plugged, likely a crystalization of fluid in the lines and very possible cracked lines as well. these new systems are definitely not proven or reliable, really makes me fume that after spending mega money this crap shuts down so many scenarios
 

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crystalizing seems to be a big problem with DEF systems. On my S-77 for winter storage we would drain the tank then rinse it with distilled water otherwise small amounts of DEF will evaporate and leave the chunks like fertilizer. Now AGCO tells us to store the machine over winter with the DEF tank completely full so there is not any area for air in the tank. I hope the lines and tank can take it when the temp gets 20 below.

Damned liberals......we can thank them that we have to use this crap. Do you know that the combines shipped over seas don't have this DEF system? Atleast that was the case in 2012 & 2013. Sure wish I knew how to program the engine to not have to mess with that crap. But that is just part of the Hopey/Changey, Yes We Can government we elected!
 

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Discussion Starter · #6 ·
Got the head unit out of the def tank( with some help from dealer mechanic, thank you Les!!) Put new head unit in and re-connected def lines and coolant lines, and no more error code! Woo Hoo!

Will check the breather filter and look for dirt in the breather hose though as a double check. Thanks for the recommendation.

Given the winter we had here in Alberta last year, not surprised a def line might freeze solid and crack. -40 Celsius several times and week long -30 nights. Def wasn't meant for our winters. Think we will be draining tanks after harvest this year.

Thanks again to those who replied.

Good luck in your harvest.

Steve
 

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That's why I'm afraid of newer equipment. I've also heard that some of the new engines need to filter diesel down to 2 microns. It comes off the bulk truck at 10 microns. Systems like this might work well in the laboratory but not in our dirt/dust/freezing temps.

Good to hear you got going again, though. Good luck with harvest.
 

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Discussion Starter · #8 ·
Maybe it hasnt cracked from freezing farmerjones, it may be cyrstals left behind from when the def evaporates if the lines are emptied when the engine shuts down. I don't know for sure. Our filter on the pump seemed clean enough but we changed it too. Still had the error code at that point. Before removing the head unit, we had drained some def out of the tank and it looked as clear as when it went in. Maybe the little mesh bag/screen at the bottom of the head unit was plugged. In any event, problem solved for now.
 

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the instructions tell you to remove e filter and inspect it,,,, and then install a new filter, do not reuse the old one, do not know why they would not just say remove and replace it, and yes the filter works, but as mentioned previously the crap crystalizes and that is what the filter is there for. regardless of the pump operating in reverse and purging the lines empty on shut down there is always droplets in low points and such that will over time evaporate and cause crystal growth. one more nail in the coffin, one more reason to shut down an otherwise operable machine at the most critical time....what a load of crap they force down our throats, and at our expense, just so the rest of the world can pollute willy nilly, that is progress for you. not only do we use up even more resources, we compound our lack of efficiency and production and thus become overpriced and our governments look to importing our food from more favorable priced countries...
 
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