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SCR,DPF,DOC ohhh my


moonsetter
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Ok so we have a whole new batch of issues with the CHU613 mack trucks(2013, average 200k miles). the SCR system is causing a bunch of issues. we are a small shop and lack all the big boys training. so we have to figure out thing on our own. First of all the DPF filter needs to been cleaned and baked every 4500 hours. Second the DEF pump is a heap of plastic junk that may or may not work right out of the box. The DEF filter needs to be changed every 50,000 miles. There is a DOC/muffler that sits atop the DPF, and according to one Mack service department, "Just spray it out with a steam cleaner, then let it air dry." I didn't bite. And we wont be putting any water on the DOC/muffler. still the SCR is about the biggest piece of crap ever introduced into trucking industry. only shy to all the different computers they have managed to install on a truck. i can only hope that my guys stay sharp and continue to read up on this tremoundously horrific addition that is meant to produce near 0 emmisions. i do hope that this helps someone. i did a search though the forums and could find that anyone had made mention of the SCR or the trouble that they create on the truck. i do wish that someone would create a thread that has more experiance than i do. and in closing "IF IT SMOKES, ITS BROKE." a different Mack service tech.

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You can feel comfort in knowing that its not just a Mack/Volvo thing, EVERYONE is having issues with these systems. There is a tremendous amount of technology going on there in a heavy duty application, problems are bound to happen. Its tough enough in a large dealer network with diagnostic software and factory technical support to solve some of these after-treatment issues, but to be an independent trying to work on this stuff has got to be a hair pulling experience.

On catalyzed systems the most common issues I see that causes SCR derate is bad DEF pumps and Nox sensors with a few EGR valve and/or EGR diff. psi sensor/veturi issues here and there. 7th injector/nozzels can still be an issue, when they get dirty they create all sorts of problems.

On the non catalyzed SCR systems (trash trucks) I have replaced quite a few atomization modules and flame temp sensors. Luckily we don't see these all that often.

We send DPF filters out to a local radiator shop that uses approved cleaning equipment. They flow test after cleaning and if it passes certain EPA flow requirements then it is reused. If not we sell the customer a new DPF filter.

On non SCR ('07 emission) with the catalyst before the DPF filter, when it gets face plugged (dirty 7th injector) we use a piece of cardboard and lightly scrape off the soot and then blow out the catalyst.

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We have truck running here with 800,000 to 900,000 miles on then with the orignal DPF filters and have never been cleaned. We check the flow/back pressure and still good. Dont believe the hype of 4500 hours. Here at our dealership we maybe change 2 DEF pumps a month in the winter ( freeze and bust) and maybe 1 in the summer. Mostly NOX sensors we see go bad and a few DEF dosers too. The EGR diff sensor can go bad/ get clogged and cause DPF/SCR problems down the road. Im really shocked that we dont have more problems than we really do.

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We've had a few minor problems with our trucks and my father who owns them will get upset about it ,then he remembers back and looked into his paper work and admitted that he had almost or as many little issues with superliners he bought new in 89 ,92 and a CL he bought in 97 and a ch in in 2000 . the technology is scary but I think they keep improving it

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fwiw.. My time before working for a Mack shop was endlessly spent swapping the old, NON-SCR dpf's around like hot cakes for cleaning, changing cracked ARD heads, and every egr issue you can imagine.

The technology has come a long way, keeping the DEF from freezing in the pump goes a long way to prevent failure, beyond that it's mostly NOx sensors and EGR delta-p's.

Paccar (engines) and Detroit have the same variety of issues.

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  • 1 year later...

Whoever said "they're not really that bad" can shove it. These are the absolute worst things to happen to trucking -- and our ability to even make a living. When we added EPA 10 trucks with DPFs and SCRs to our fleet, we spent the next 11 months having to learn about them almost daily as one visit to a shop after another sucked away every bit of the truck's revenue and more. Nobody deserves this. These systems are simply not reliable, and even dealer techs misdiagnose their problems regularly, meaning one derate after the next, and one return visit after the next. It's just so fun having your credit cards maxed out and your home equity maxed out to keep a few fault codes away. You don't clean the air by bankrupting hard-working people. The morality of that idea is nonexistent. 

Edited by Daddy
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Whoever said "they're not really that bad" can shove it. These are the absolute worst things to happen to trucking -- and our ability to even make a living. When we added EPA 10 trucks with DPFs and SCRs to our fleet, we spent the next 11 months having to learn about them almost daily as one visit to a shop after another sucked away every bit of the truck's revenue and more. Nobody deserves this. These systems are simply not reliable, and even dealer techs misdiagnose their problems regularly, meaning one derate after the next, and one return visit after the next. It's just so fun having your credit cards maxed out and your home equity maxed out to keep a few fault codes away. You don't clean the air by bankrupting hard-working people. The morality of that idea is nonexistent. 

And not to mention nobody can afford to fix these trucks after the warranty is out. 2nd and 3rd owners need not apply.

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I'm leased on with a guys trucking company & he has several different brands running; he's had more problems with the Paccar engines; the Volvo has given the least amount of emission problems; BUT the INJECTERS & camshafts & the bullgear stuff is something Mack/Volvo has got that they should take care of; in my opion; he's got 1 Volvo that Volvo put injecters in with less than a year worth of running that needs them again; can kind of understand the external emission stuff; but the internal stuff is really on them; in my opion!

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15 hours ago, Underdog said:

And not to mention nobody can afford to fix these trucks after the warranty is out. 2nd and 3rd owners need not apply.

As I have said before on here, Owning a new truck is now like owning a BMW ( or insert any European auto maker). You better get extended warranty or ditch it as soon as the  warranty runs out.  I"ve seen lots of 2008 and even 2010  trucks junked and sold for parts because of the cost of repairs were too high. 

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