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Help with diagnosis please: 6.7 Cummins, new turbo, intermittently blowing blue smoke

168 Views 5 Replies 2 Participants Last post by  mrldcty
2007 3500 dually, 6.7 Cummins, 135K miles: Last year my turbo went out so I did some research and replaced it with an ATS Aurora 4000. I also did an EGR cleanout at that time. It was quite a tussle getting it in and out, but once it was installed, it ran awesome for a few months. Loads of power, mileage was up, and I was a happy camper. At the end of the summer, I was stopped at a stoplight and noticed blue smoke coming from under the right side of the engine compartment. I jumped out to have a look but by the time I got it in park and the hood up, it had stopped. It continues to get worse, and happen more often but I haven't been able to diagnose where it is coming from. I'm hoping someone on here can offer some suggestions on what it might be. Here are some other observations/thoughts:

1. It's blue smoke, so my first thought was oil leak. I tried tightening the fittings that I can get to without removing the intake and battery. I got a small turn on one of the banjos, but everything else seems snug. Also, it's not down on oil. Oil pressure is good.
2. There is black soot in various places on the passenger side of the engine, but nothing that would indicate where it is coming from.
3. Truck sounds and runs great, tons of power and not getting hot. Starts right up.
4. No codes are being thrown, at least as far as my ODBII reader can tell.
5. Sometimes it smokes like crazy and other times nothing, which makes me wonder if it has something to do with the EGR cycle.
6. My mileage seems to be inching down. While experimenting with gearing, I have noticed that it gets better mileage if I run it at 2000 RPM or above. Like 2 miles/gal better! Is this normal? Or perhaps the ECU calculates mileage incorrectly when running in lower gears than the auto trans would?
7. If I stop and I see it smoking, if I put it in park, it stops. I have tried leaving it in neutral and even in drive with the brake on, but I can't seem to get out there fast enough to catch it in the act... so strange! I even had a buddy drive it with me as the passenger and when it smoked, I jumped out and still didn't catch it. Other times, I think... oh it will stop, but it smokes and smokes until I try to look at it. It's as if it's messing with me! Is there some ECU controlled cycle that would sense when it isn't under load or in P or N that could explain the intermittent nature of the smoke?
8. Exhaust connections seems solid and the air filter doesn't look particularly fouled or black (I changed it recently).
9. Longer freeway drives seems to reduce the frequency and volume, but this is really anecdotal evidence because it may smoke a whole bunch while on the freeway and get blown out the back such that I don't notice it. I haven't noticed any smoke trailing behind the truck when in motion, but it may be that it simply isn't enough to see.

I don't think the dealer will touch it now that I've put an aftermarket turbo in it. Does anyone have a recommendation on diagnostic devices to help figure this out? I suspect my OBDII reader may not be giving me all the codes.

Also, if anyone knows a reliable diesel mechanic near North Bend WA... I'm all ears.

Thanks in advance for any suggestions!
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"Soot all over the passenger side of the engine".
You've definitely got a gasket leak somewhere in that area.
Your blue smoke is probably happening when you're in regen and the unburnt diesel is leaking out and when you stop, it suspends the regen.
It's getting worse because the gasket is degrading so you need to start looking for the bad gasket(s).
(The rear egr cooler flange is a common one)
 
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Discussion Starter · #3 ·
I was wondering if the blue smoke might be related to regen... just wouldn't have thought it would leak out so far forward given where the regen is located. Also, the fact that it is intermittent and stops when I stop fits that theory too.

Thanks for that... I put new flange gaskets in when I replaced the cleaned EGR cooler so I may have got one misaligned or cracked. I probably need to pressure test the cooler when I take it out again too.
 

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Your cooler is fine. You'd be seeing coolant in the exhaust if it had a leak.

Regen starts with the exhaust stroke fuel injection to each cylinder. This is done so that the unburnt fuel will travel thru the turbo to the exhaust and burn for the regen.

It could be as easy as tightening the bolts on the flanges, crossover tube and turbo mounting bolts.

Or it could mean new gaskets which is a pita.
 

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Discussion Starter · #6 ·
Anyone have input on item 6 from my list?

6. My mileage seems to be inching down. While experimenting with gearing, I have noticed that it gets better mileage if I run it at 2000 RPM or above. Like 2 miles/gal better! Is this normal? Or perhaps the ECU calculates mileage incorrectly when running in lower gears than the auto trans would?
 
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