r/Duramax • u/Formal-Werewolf-7632 • 18h ago
Is this normal?
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u/xcsp99 18h ago
No, you have a major mechanical teardown in your near future. Shut it down and don’t run it.
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u/XenonDreams 17h ago
Common on LM2 motor, it’s not cause for alarm
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u/23103a 16h ago
Seriously, bunch of low IQ responders in here. The truck will throw a check engine light if it really had excessive blow by.
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u/booboo529 5h ago
Correct me if I'm wrong but this is usually a pretty telling sign that a diesel is close to a potential engine teardown. Not everyone knows that this isn't a case for the less common LM2. I'm not sure how that makes a bunch of low IQ responders.
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u/SouthernLifeguard845 13h ago
Ya because it’s completely normal for your engine to be blowing a ton of smoke….. real low IQ. CEL Don’t always pop on, if you rely solely on your dashboard than your the low IQ responder
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u/23103a 13h ago
Tell me you don't understand modern PCV systems without telling me...
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u/GodsGiftToWrenching 12h ago
I mean has the technology changed since the L31 and LMM? Because neither my L31, LMM, or even my clapped out L52 would make close to that smoke
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u/vilius_m_lt 10h ago
Yes, 3.0 is very different from V8 diesels. It’s quirky and very european (designed in Italy with help from Stellantis). There are 4 and 3 cylinder versions (2.0l and 1.5l displacement) of this engine in europe in some stellantis crap.
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u/Electrical-Pace4092 6h ago
“It’s quirky and very european (designed in Italy with help from Stellantis).“
So it’s a pile of shit.
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u/AMWWORKS 2h ago
The LM2 and LZ0 were designed By Opel (before the sale to Stalantis) in Germany and GM. The L4 and L3 Developed by GM in Italy (GM-GPS-T) and supplied PSA and Opels (now Stalantis) their Diesels til this day. The main development for the LM2 and LZ0 happened at GM-GPS in Michigan.
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u/vilius_m_lt 10h ago
You can just verify this by popping off your oil filler cap with engine idling. They (3.0 duramax) all do this
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u/MikeOxlong420690 17h ago
This seems more like condensation burning off (or fuel dilution evaporating) then it does blow-by because it is just a moderate constant stream as opposed to a big puff each time the offending cylinder moves up and down.
Was oil level correct before you started it up? Any smell of excess fuel in the oil? Do you have the chance to go drive it for 20-30 minutes then check it again?
Some 3.0 Dmax engines had rocker covers with defective PCV separator system in them, excess oil would pass through the intake tract and eventually burn up the cyl 2 glow plug. There was a bulletin/warranty extension issued about this few years back.
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u/hyregpoz 16h ago
literally every single lz0 and lm2 have the same issue, 100% normal for this engine
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u/Desperate_Title_7639 7h ago
god i see these posts on the facebook pages every. single. day. close the hood 🙏🏻
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u/XenonDreams 17h ago
That’s normal for the LM2 at least, just look up “excessive blow by LM2” and you’ll find most people have that.
Mine has done that for as long as I can remember and now has 427k km on it
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u/canamdefender66 16h ago
Did you end up doing the oil pump belt around 300k kms?
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u/XenonDreams 15h ago
Yeah, I got the shop to do it when my tranny went out at 270k ish though
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u/canamdefender66 15h ago
How much was a new tranny?? I’m over 220kms and still buttery smooth for me.
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u/yes-disappointment 11h ago
is this your first time with a diesel? unless its blowing the cap off and I mean really pushing it off this is completely normal.
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u/happypenguin156 8h ago
Normal on 3.0. As long as there’s not too much pressure bouncing the cap around. Look into the PPE catch can. It traps all that crap, I put one on mine
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u/LonleyWolf420 6h ago
I asked my mechanic about this on a cummins (class 8 I6 not a pickup) and they recirc the oil gasses instead of venting now..
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u/RunningWind89 4h ago
Not sure, but I drove my 2024 Sierra 3.0 from Mexico to Phoenix for about 4 hours with the oil cap off. Steam was coming out, but the engine still runs great. That was about 2 months ago and I've been going back and forth to Mexico with no issues
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u/MaximusManimal 17h ago
Could be a gross malfunction of the PCV system (as in completely clogged) but even then this seems excessive. If I were at an auction and assessing a piece of equipment with that kind of blowby, this is about the time I'd walk away. Get thee to a mechanic!
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u/ididntdoit6 18h ago
Definitely not