hummer h3 valve cover
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Joined: May 2016
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Senior Member
Joined: Jul 2012
Posts: 8,907
From: C-Town
Crankcase Ventilation System Inspection/Description
Crankcase Ventilation (CV) System Inspection
Fig. 27: View Of Crankcase Ventilation SystemCourtesy of GENERAL MOTORS CORP.
- Test for vacuum at the positive crankcase ventilation (PCV) dirty air hose (2) where it connects to the vacuum orifice tube (5) in the camshaft cover. There should be manifold vacuum present at the hose (2). If there is no vacuum, inspect for a plugged hose, leaking hose or a plugged intake manifold passage.
- If oil has accumulated in the air cleaner resonator (1), inspect for the following conditions:
- Plugged vacuum orifice tube (5) in the camshaft cover
- Plugged, restricted or leaking PCV dirty air hose (2)
- Plugged or restricted intake manifold passage (3)
- Excessive crankcase pressure or blow-by, refer to Engine Compression Test
- Additional items to inspect:
- Plugged or restricted vacuum tube (4) in the camshaft cover
- Plugged or restricted PCV fresh air hose (6)
- Plugged or restricted passage in the air cleaner resonator (1)
- Inspect the cam cover, the oil pan, engine front cover and other sealing areas for leaks
Results of Incorrect Operation
A plugged crankcase ventilation system may contribute to the following conditions:- A rough idle
- Stalling or a slow idle speed
- Oil leaks
- Oil accumulation in the air cleaner resonator (1)
- Sludge in the engine
- A rough idle
- Stalling
- Unstable idle speed
Senior Member
Joined: Feb 2014
Posts: 468
From: north Alabama
LOL I always that that provided filtered air to the cylinders. My bad. 
I do appreciate the CV description - very handy. 👍
I do appreciate the CV description - very handy. 👍
Last edited by Justinh; Nov 10, 2024 at 12:25 PM.
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