2005 6.0 Lq9 PCV blockage - The 1947 - Present Chevrolet & GMC Truck Message Board Network

OldCreek · 11-18-2025, 08:50 PM

I put an LQ9 from a 2005 Cadillac Escalade in my K5 roughly 15 years ago. I've only put around 5,500 miles on it since then. I have not done yearly oil changes...

I'm not much of a diagnostician but it sounds like the PCV and increased crankcase pressures that are causing my problems...

Recently, it is idling rough and driving even worse. No codes are coming up. It smells rich but it always has and I'm not running cats. There was some noise as if there was an exhaust leak and I've noticed more leaking of engine oil (haven't looked close enough to see where.) I haven't noticed any significant oil consumption but then again I'm not driving it that much.

During my trouble shooting, I pulled the MAP sensor and noticed oil on it. After replacing with a new one the motor ran well for a few minutes but symptoms appear to be returning. My online research leads me to PCV failure/blockage. And further research shows that my engine doesn't have a PCV valve, per se, but has a fixed orifice valve/nipple.

So, is it likely that the valve cover baffle drainage holes are blocked and the PCV nipple is blocked, too? Is it simple enough to clean out the drainage hole and maybe even drill it out to roughly 1/4"? And maybe add some drainage holes to the baffle? Or, should I just get the new updated valve cover? And, maybe drill that out a little to ensure proper drainage? No, I won't drill the orifice itself, if that's even possible.

Would you install an inline oil catch can, too?

Yes, better oil change schedule may be helpful, too.

I'll likely pull the valve cover this weekend...

Thanks,

Wil

OldCreek · 11-19-2025, 03:43 PM

Perhaps this post is better off in the Engines and Drivetrain section? Hatzie, I'm okay with moving it...

**hatzie** · 11-23-2025, 07:35 PM

You can definitely add drainage holes to the valve cover baffles.
https://67-72chevytrucks.com/vboard/...d.php?t=820356

GM has updated valve covers to mitigate oil usage on the Pre-2009 LS engines.
This BITOG thread has pictures of the updated baffles.

https://bobistheoilguy.com/forums/th...nstall.251305/

11-18-2025, 08:50 PM	#1
OldCreek Registered User Join Date: Jan 2007 Location: Central Coast California Posts: 1,035	2005 6.0 Lq9 PCV blockage I put an LQ9 from a 2005 Cadillac Escalade in my K5 roughly 15 years ago. I've only put around 5,500 miles on it since then. I have not done yearly oil changes... I'm not much of a diagnostician but it sounds like the PCV and increased crankcase pressures that are causing my problems... Recently, it is idling rough and driving even worse. No codes are coming up. It smells rich but it always has and I'm not running cats. There was some noise as if there was an exhaust leak and I've noticed more leaking of engine oil (haven't looked close enough to see where.) I haven't noticed any significant oil consumption but then again I'm not driving it that much. During my trouble shooting, I pulled the MAP sensor and noticed oil on it. After replacing with a new one the motor ran well for a few minutes but symptoms appear to be returning. My online research leads me to PCV failure/blockage. And further research shows that my engine doesn't have a PCV valve, per se, but has a fixed orifice valve/nipple. So, is it likely that the valve cover baffle drainage holes are blocked and the PCV nipple is blocked, too? Is it simple enough to clean out the drainage hole and maybe even drill it out to roughly 1/4"? And maybe add some drainage holes to the baffle? Or, should I just get the new updated valve cover? And, maybe drill that out a little to ensure proper drainage? No, I won't drill the orifice itself, if that's even possible. Would you install an inline oil catch can, too? Yes, better oil change schedule may be helpful, too. I'll likely pull the valve cover this weekend... Thanks, Wil __________________ 1972 K20 Suburban 5.7/700r4/NP205 Dana 44/H052 Sold 1972 C10 5.3L/4L60E 12bolt 5Lug - Sold 1971 K5 Blazer 6.0L LQ9 4L60E NP205 Dana 44/H052!!! 1970 K3500 1ton CrewCab 8.1L/Allison1000/NP205 Dana 60/14B!!!! - Sold 1988 V30 CCLB 7.4L/TH400/NP205/Dana 60/Dana 70!!! (Sold) 2003 K2500HD 8.1/Allison1000/NP263 Last edited by OldCreek; 11-18-2025 at 09:00 PM.

11-19-2025, 03:43 PM	#2
OldCreek Registered User Join Date: Jan 2007 Location: Central Coast California Posts: 1,035	Re: 2005 6.0 Lq9 PCV blockage Perhaps this post is better off in the Engines and Drivetrain section? Hatzie, I'm okay with moving it... __________________ 1972 K20 Suburban 5.7/700r4/NP205 Dana 44/H052 Sold 1972 C10 5.3L/4L60E 12bolt 5Lug - Sold 1971 K5 Blazer 6.0L LQ9 4L60E NP205 Dana 44/H052!!! 1970 K3500 1ton CrewCab 8.1L/Allison1000/NP205 Dana 60/14B!!!! - Sold 1988 V30 CCLB 7.4L/TH400/NP205/Dana 60/Dana 70!!! (Sold) 2003 K2500HD 8.1/Allison1000/NP263

11-23-2025, 07:35 PM	#3
hatzie Moderator Join Date: Oct 2008 Location: Wentworth, NH Posts: 5,049	Re: 2005 6.0 Lq9 PCV blockage You can definitely add drainage holes to the valve cover baffles. https://67-72chevytrucks.com/vboard/...d.php?t=820356 GM has updated valve covers to mitigate oil usage on the Pre-2009 LS engines. This BITOG thread has pictures of the updated baffles. https://bobistheoilguy.com/forums/th...nstall.251305/ __________________ 1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials... 1973-1991 GM Light Truck Service, Unit/Overhaul, Wiring Manuals, Parts Books and Some 1968-1999 GM Service Training textbooks in PDF 1988-1998 GMT400 CK service manual project 1988-1993 GMT400 CK parts books. 1967-1972 GM Light, Medium, & Heavy Truck Service Manuals in PDF Please include at least the year and model in your threads. It'll be easier to answer your questions. And please let us know if and how your repairs were successful.



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