Ok guys we have been seeing alot of maxx7s/6.4. We have had a string of issues with these engines with fuel in oil, mechanical issues, cam issues, injector issues and the biggest and most important is the aftertreament. I have seen in the week 3 DOCs plugged solid and causes fuel in oil and engine failures. This is a bad problem and i urge 6.4 owners to remove it for your engine sake and yours!!!! The DPF was also clogged too with no indication of issues before that! Any ideas why? I know the answer lets see if anyone else can figure it out for some fun.

 

why on what part?
they are overfull do to excessive regen.
wait till you see them burn the whole left bank. from oil/fuel in the cac.

whay are they going in to regen so often?
I dont know about what you are seeing but are are from a few things.
1) excessive engine hours and idle time causing the doc to plug and regen not being able to complete
2) lack of proper maintance.
3) dirty maf and after market air filters.

 

Regens are being complete on these units as per pids. Oil chanegs are a little far aprt at 10000 miles or 5 months for this bus company excess of 300 plus in my area. heres my idea on why these issues are occuring. Number #1 is heat there is no temp sensor before the doc there for the clogged DOC is making alot of extra heat. #2 bad programming and the learning curve for this new stuff and not taking in consideration all the different applications trucks can have. The reason its making oil which navistar will not realese to me and have tried is the doc dpf as we know is already a retrictive piece. When they get clogged up the backpressure keeps the better part of aftertreatment fuel in the engine and pushing it past the rings. Me and another guy figured this issue out ourselves this week after navistar called it quits and said return it to serice with the issue still there. The DOC on the bellows and down pipe was clogged solid and the engine compression on several cly was 100psi below the others. I dont know whats going on with these engines but they better figure it out casue they are starting to make the 6.0/365 look like an awsome engine to me now. since its been awhile since i done anything else other than change engine form lifter/cam failures. These 6.4s i think are heading for disaster from the aftertreament so get that junk off them!!

 

When I first got mine, some of the information provided on the DVD with the truck indicated a passive regen would happen when you are working this motor.

I don't think so, if that was the case then why would there be a need for the active regens every 150 or so miles when pulling hard.

So there is certainly something going on there.

 

Something is up casue the doc on my failed bus has about 3 inchs of carbon caked on the majority of it. Also I meant pressure sensor not tiemp sensor. The doc should have a diff pressure sensor to try and measure the differences and its not the dpf thats the issue it works good its the DOC

 

I hate to but my head in with the pros, but, Senix and I share an opinion on these things. The 6.4 stays healthy when it is worked. Long interstate runs at 70% or more load and all the emissions aftertreatment stuff works as advertised with no problems.

My 6.4 has 145,000 miles on it, all interstate and towing miles. I really thought I would have DPF/DOC issues by now but they remain clean as a whistle. Those bus motors while running loaded stay in a stop and go pattern which obviously kills the aftertreatment systems.

I agree that it's a poor design, very few people drive 450 miles at 70 MPH every other day so very few people will probably get good reliable performance out of the motor.

 

not 'poor', more 'wrong' design for the conditions. Or wrong use of the engine for the particular solution requirements.

and sorry, what is the definition of 'DOC'? I got DPF, EGR, CAC...

sam

 

That would be the catalytic converter

 

Nope! Diesel Oxidation Catalyst. Look under your cowl, behind the turbo, you can see it.

 

thanks.. got it

if that is clogged, so close the the engine, then the airflow rate has to be restricted pretty heavily.. and/or the temps are too low which allows accumulation..

Sam

 

The sole job of the DOC is to dry out the exhaust before it goes to the egr coolers. The exhaust flow it has, is a bypass off of the pass side exhaust flow. Its flow doesn't go through the turbo.

 

I read that statement as the edoc, not the doc in the down pipe.

 

ok so i was talking to 2 guys from navistar today. They said throughout the US the biggest issue these engines are having is clogged DOCs causing multiple issues like fuel in oil, aftertratment issues ect. We was talking and yes they do run all 8 cyl on on regen now. Before it would alternate as per dpf soot load. They have since changed programming though. We was also talking about why they didnt put a aftertreatment inj in the exhaust like the big bores do. They both said they have been trying to get a retro fit kit or a design change with no luck. The biggest thing they toldme though was to change your oil as often as possible since you will always get a certain amount of fuel in the oil from regen bypassing rings with gets worse with engine age and not running it hot.


I also tried posting this pic of the doc but couldnt get it to work

 

We have one of these engines in a 65 passenger school bus. After 15,000 miles I can report that it has performed flawlessly but we are a rural school so we don't just putt around town.
Our dealer says in order to minimize DPF problems, oil changes should be done at 250 hours and if idling engine to ramp up rpms to 1500.

 

Is there a way to get this stuff off without going to a higher hp tuner? I hate to make the engine work harder then stock. I don't need extra HP.
I hope someone comes up with aftermarket stuff.