Hummer H3. Manual — part 284

CRANKCASE VENTILATION SYSTEM INSPECTION/DESCRIPTION

Crankcase Ventilation (CV) System Inspection

10

Higher than recommended fluid
pressures

Plugged or malfunctioning fluid
filters or pressure bypass valves

Plugged or malfunctioning
engine ventilation system

Improperly tightened or
damaged fasteners

Cracked or porous components

Improper sealants or gaskets
where required

Improper sealant or gasket
installation

Damaged or worn gaskets or
seals

Damaged or worn sealing
surfaces

2. Inspect the engine for customer

modifications.

Is there mechanical damage or customer
modifications to the engine?

Go to Step 11

System OK

11

Repair or replace all damaged or modified
components.
Does the engine still leak oil?

Go to Step 1

System OK

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3

Fig. 27: View Of Crankcase Ventilation System
Courtesy 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:

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3

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 leaking hose may contribute to the following conditions:

A rough idle

Stalling

Unstable idle speed

The crankcase ventilation system has no serviceable components so no maintenance of the system
is required.

DRIVE BELT CHIRPING, SQUEAL AND WHINE DIAGNOSIS

Diagnostic Aids

A chirping or squeal noise may be intermittent due to moisture on the drive belts or the
pulleys. It may be necessary to spray a small amount of water on the drive belts in order to
duplicate the customers concern. If spraying water on the drive belt duplicates the symptom,
cleaning the belt pulleys may be the probable solution.

If the noise is intermittent, verify the accessory drive components by varying their loads

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3

making sure they are operated to their maximum capacity. An overcharged A/C system,
power steering system with a pinched hose or wrong fluid or a generator failing are
suggested items to inspect.

A chirping, squeal or whine noise may be caused by a loose or improper installation of a
body or suspension component. Other items of the vehicle may also cause the noise.

The drive belts will not cause a whine noise.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

2: The noise may not be engine related. This step is to verify that the engine is making the
noise. If the engine is not making the noise do not proceed further with this table.

3: The noise may be an internal engine noise. Removing the drive belts one at a time and
operating the engine for a brief period will verify the noise is related to the drive belt. When
removing the drive belt the water pump may not be operating and the engine may overheat.
Also DTCs may set when the engine is operating with the drive belts removed.

4: Inspect all drive belt pulleys for pilling. Pilling is the small balls or pills or it can be
strings in the drive belt grooves from the accumulation of rubber dust.

6: Misalignment of the pulleys may be caused from improper mounting of the accessory
drive component, incorrect installation of the accessory drive component pulley or the
pulley bent inward or outward from a previous repair. Test for a misaligned pulley using a
straight edge in the pulley grooves across two or three pulleys. If a misaligned pulley is
found refer to that accessory drive component for the proper installation procedure for that
pulley.

10: Inspecting of the fasteners can eliminate the possibility that a wrong bolt, nut, spacer or
washer was installed.

12: Inspecting the pulleys for being bent should include inspecting for a dent or other
damage to the pulleys that would prevent the drive belt from not seating properly in all of
the pulley grooves or on the smooth surface of a pulley when the back side of the belt is
used to drive the pulley.

14: This test is to verify that the drive belt tensioner operates properly. If the drive belt
tensioner is not operating properly, proper belt tension may not be achieved to keep the
drive belt from slipping which could cause a squeal noise.

15: This test is to verify that the drive belt is not too long, which would prevent the drive
belt tensioner from working properly. Also if an incorrect length drive belt was installed, it
may not be routed properly and may be turning an accessory drive component in the wrong
direction.

2007 Hummer H3

2007 ENGINE Engine Mechanical - 3.7L - H3