LB7: Oil vent

TheBac

Why do I keep doing this?
Staff member
Apr 19, 2008
15,400
1,676
113
Mid Michigan
Could simply be a plugged up PCV system, but GM says the valve itself is not serviceable, so I have no idea how you'd check it.
 

motoking_1990

Active member
May 9, 2011
1,957
5
38
Terre Haute, IN
Ahhhh ok I will check into that. I would've checked it earlier if my phone wasn't dead and I could had read this. Are there one of these on each valve cover? Thanks guys


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AKlowriderZ71

New member
May 14, 2012
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Wyoming
Yes, one on each side.

If they both check out okay, then follow the hoses to the black jug on the front passenger side of the engine. There should be 2 more hoses coming off that jug. The large one vents down there by your oil pan. If the jug fills up, that's where it comes out. You should also find a smaller diameter hose coming off the bottom. The smaller hose connects to a small nipple on the right front side of the engine, near the balancer. Make sure that hose is connected, but also make sure that hose isn't clogged or kinked. That is the drain-back for the PCV jug. If it can't return the oil, the jug fills up.

I'll see if I can find a pic...
 

motoking_1990

Active member
May 9, 2011
1,957
5
38
Terre Haute, IN
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motoking_1990

Active member
May 9, 2011
1,957
5
38
Terre Haute, IN
This is the hose I'm talking about I can't even see where it leads to. But the hose you were describing is intact and so is the brass serviceable pcv valve. As you can see its made quite a mess under there. It has to be leaking when its running cause I don't have any spots in my driveway. I really can't see up in there at night all that well but it might lead to that box you are talking about.
 

bhassett110

New member
Mar 11, 2015
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Newport mi
New to the forum. But did you ever figure out what's causing this mines doing the same thing under high positive pressure but im running about 28psi of boost . Is this normal because the pcv system was not designed for that boost or no. Not much oil loss just makes a mess.
 

chevyburnout1

Fixing it till it breaks
Aug 25, 2008
2,368
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38
Berthoud, CO
I had one truck come through the shop with this problem. No blowby at idle and wouldn't leak oil out until under heavy load. Ended up cleaning out the little oil drain hose and replacing the oil check valve.
 

motoking_1990

Active member
May 9, 2011
1,957
5
38
Terre Haute, IN
I took the cover off and cleaned it out along with cleaning the valve. I haven't really looked under it lately to know if it has been leaking been too busy with the topside. I will check tomorrow when I finish up hooking up the wiring harness and report back.