Sep 30, 2014
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In the Shop

RSS By: Dan Anderson, Farm Journal

As a farm machinery mechanic and writer, Dan brings a hands-on approach that only a pro can muster. Along with his In the Shop blog, Dan writes a column by the same name as well as the Shop Series for Farm Journal magazine. Always providing practical information, he is a master at tackling technical topics and making them easy for all of our readers to understand. He and his wife, Becky, live near Bouton, Iowa.

Diesel Exhaust Fluid, Friend AND Foe

Aug 09, 2014

 You don't have to like Diesel Exhaust Fluid (DEF), but you're going to have to accept it. In order to meet Environmental Protection Agency regulations, many engine manufacturers are using Selective Catalytic Reduction (SCR) systems to reduce diesel exhaust emissions. Injecting DEF into an SCR exhaust system is one of the steps to reduce diesel exhaust fumes to a level where they are purportedly cleaner than the air in downtown Los Angeles on a smoggy day.

So here's the good news about DEF, aside from its benefits to the environment: When everything is working correctly, all you have to do is keep the special DEF tank filled. Computers and components do all the rest. The operator just has to tune in their favorite radio station and drive.

But here's the bad news about SCR/DEF systems: they are EXPENSIVE. We're talking about tens of thousands of extra dollars added to the purchase price of a truck or tractor. For you truck drivers for whom weight is an issue, I'm told that SCR systems add a thousand or more pounds to the base weight of the truck, therefore reducing your potential legal load capacity. There's also an initial "get acquainted" cost of adding DEF storage tanks and transfer pumps for anybody who purchases a machine that requires DEF, because DEF requires special tanks, special pumps and sanitary handling practices. Everything is cool after those initial costs--until something goes wrong with the SCR system.

There are two costs associated with repairing a malfunctioning SCR system. The first is the cost of components, There are a lot of computers, sensors and specialized gadgetry on SCR systems. With sensors costing $150 and more each, and the main catalytic converter retailing for more than $10,000, it can be expensive to replace failed components. Then, there's the cost of diagnosing and physically replacing failed parts and pieces. It's going to take mechanics a couple years to learn the tricks and shortcuts to diagnose and repair SCR sytems.

So, the good news is that most of the time, SCR exhaust systems will operate seamlessly in the background, once you get past the initial purchase price(s). But hold onto your wallet if something goes wrong and repairs are required. Mechanics don't like it any more than you do, but it's the law, so we might as well get used to it.

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