2007 ISUZU KB P190 belt

Engine Mechanical – V6 Page 6A1–45

Step Action Yes No
10 Inspect for missing, loose or incorrect fasteners.
Did you find any missing, loose or incorrect fasteners? Go to Step 11 Go to Step 12
11 Tighten any loose fasteners to the torque specification as provided in
provided in 6. Torque W rench Specifications.
Replace any incorrect or missing fasteners.
Did you complete the repairs? Go to Step 15 —
12 Inspect for a bent pulley. Did you find any bent pulleys? Go to Step 13 Go to Step 14
13 Replace bent pulleys as required. Did you complete the repair? Go to Step 15 —
14 Replace the accessory drive belt, refer to 3.5 Accessory Drive Belt.
Did you complete the repair? Go to Step 15 —
15 Reinstall the accessory drive belt and operate the system to confirm the repair.
Did you correct the chirp noise? Accessory drive
system OK Go to 2.2
Symptoms, and restart the
diagnosis
Drive Belt Squeal
Definition
Accessory drive belt squealing can be defined as a loud screeching noise caused by a slipping drive belt. Belt squeal is
unusual in multi-rib belts. Drive belt squeal generally occurs when a heavy load is applied to the drive belt, such as an
air-conditioning compressor engagement, snapping the throttle, seized pulley or a faulty accessory drive component.
Diagnostic Aids
If the noise is intermittent, confirm the accessory drive components by varying their loads, making sure they are operated
to their maximum capacity. An overcharged A/C system, restrictions in the power steering pressure circuit or a faulty
generator or coolant pump are likely causes of accessory drive belt squeal.
A loose or incorrectly installed body component, suspension component or other item may be the cause of the noise.
Test Description
The numbers below refer to steps in the diagnostic table.
2 The noise may not be engine related. This step is to confirm the engine is making the noise. If the engine is not making the noise, do not proceed further with this diagnostic procedure.
3 The noise may be an internal engine noise. Removing the drive belt and operating the engine briefly will confirm whether or not the noise is related to the drive belt.
CAUTION
When running the engine with the accessory
drive belt removed, the coolant pump will not
be operating and the engine may overheat if
left unsupervised even for a short period.
NOTE
There may also be a number of DTCs set when
running the engine with the accessory drive belt
removed.
4 Confirms an accessory drive component does not have a seized bearing. W ith the belt removed, test the bearings in the accessory drive components spin free and smooth.
5 Confirms the drive belt tensioner is operating correctly. If the drive belt tensioner is not operating correctly, drive belt tension will not be maintained, resulting in a belt squealing noise
6 Confirms the belt is not too long, which would prevent the tensioner from working as intended. Also, if an excessively long belt has been fitted, it may also be routed incorrectly and may be turning an accessory drive
component in the wrong direction.

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ISUZU KB P190 2007

Engine Mechanical – V6 Page 6A1–46

7 Misalignment of the pulleys may be caused by one of the following:
• Incorrect mounting of an accessory drive component,
• Incorrect installation of an accessory drive pulley or,
• Bent or damaged pulley.
Test for a misaligned pulley using a straight edge in the pulley grooves across 2 or 3 pulleys. If a misaligned pulley is found, refer to the relevant component service information for the correct installation and removal procedures.
8 This test is to confirm the pulleys are the correct diameter and/or width. Using a known good vehicle, compare the pulley sizes.
Diagnostic Table
Step Action Yes No
1 Did you review the information provided in 2.2 Symptoms, and
perform the required inspections. Go to Step 2 Go to 2.2
Symptoms
2 Confirm the customer complaint. Is there a squealing noise? Go to Step 3 Refer to Diagnostic
Aids in this Section
3 1 Remove the drive belt, refer to 3.5 Accessory Drive Belt.
2 Operate the engine for no more than 40 seconds.
Does the squealing noise still exist? Accessory drive
system OK.
Go to 2.2
Symptoms, and restart the
diagnosis of the noise Go to Step 4
4 Inspect the accessory drive components for a seized bearing and
general malfunctions.
Did you find and correct any seized bearings or general malfunctions
in the accessory drive system? Go to Step 9 Go to Step 5
5 Test the accessory drive belt tensioner for correct operation, refer to
Accessory Drive Belt Tensioner Diagnosis.
Did you find and repair any problems with the tensioner? Go to Step 9 Go to Step 6
6 Inspect the accessory drive belt is the correct length, refer to 3.5
Accessory Drive Belt.
Did you find and repair any problems with the drive belt length? Go to Step 9 Go to Step 7
7 Inspect the accessory drive pulleys for misalignment.
Did you find and correct any misaligned accessory drive pulleys? Go to Step 9 Go to Step 8
8 Check the accessory drive pulleys are the correct size. Did you find and replace any incorrect pulleys? Go to Step 9 Refer to Diagnostic
Aids in this Section
9 Reinstall the accessory drive belt and operate the system to confirm
the repair.
Did you correct the squeal noise? Accessory drive
system OK Go to 2.2
Symptoms, and restart the diagnosis
Drive Belt Whine
Definition
Accessory drive belt whine can be defined as a high-pitched continuous noise that is most likely to be caused by a failed
bearing in one of the accessory drive components.
Diagnostic Aids
The drive belts themselves will not cause a whine. If the noise is intermittent, confirm the accessory drive components by
varying their loads, making sure they are operated to their maximum capacity. An overcharged A/C system, restrictions
in the power steering pressure circuit or a faulty generator or coolant pump are likely causes of accessory drive belt
whine.
Test Description
The numbers below refer to steps in the diagnostic table.

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ISUZU KB P190 2007

Engine Mechanical – V6 Page 6A1–47

3 The noise may be an internal engine noise. Removing the drive belt and operating the engine briefly will confirm
whether or not the noise is related to the drive belt.
CAUTION
When running the engine with the accessory
drive belt removed, the coolant pump will not
be operating and the engine may overheat if
left unsupervised even for a short period.
NOTE
There may also be a number of DTCs set when
running the engine with the accessory drive belt
removed.
4 The inspection of bearings should include the following accessory drive components: • drive belt tensioners,
• drive belt idlers,
• generator,
• power steering pump,
• coolant pump, and
• A/C compressor.
The drive belt may need to be installed and the accessory drive components operated separately, at varying loads to confirm the location of the faulty bearing, refer to the relevant Sections for component inspection and repair
procedures.
Diagnostic Table
Step Action Yes No
1 Did you review the information provided in 2.2 Symptoms, and
perform the required inspections. Go to Step 2 Go to 2.2
Symptoms
2 Confirm the customer complaint. Is there a whining noise? Go to Step 3 Refer to Diagnostic
Aids in this Section
3 1 Remove the drive belt, refer to 3.5 Accessory Drive Belt.
2 Operate the engine for no more than 40 seconds.
Does the whining noise still exist? Accessory drive
system OK
Go to 2.2
Symptoms, and restart the diagnosis Go to Step 4
4 Inspect the accessory drive components for a faulty or seized
bearings and general malfunctions.
Did you find and correct any faulty/seized bearings or general
malfunctions in the accessory drive system? Go to Step 5 Refer to Diagnostic
Aids in this Section
5 Reinstall the accessory drive belt and operate the system to confirm the repair.
Did you correct the whine? Accessory drive
system OK Go to 2.2
Symptoms, and restart the diagnosis
Drive Belt Rumble
Definition
Accessory drive belt rumble can be defined as a low pitch tapping, knocking or thumping noise heard at or just above idle,
once per rotation of the drive belt or a specific component. Drive belt rumble is generally caused by one of the following:
• pilling or strings in the drive belt grooves,
• separation of the drive belt, or
• a damaged or faulty drive belt.

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ISUZU KB P190 2007

Engine Mechanical – V6 Page 6A1–48

NOTE
Pilling is the small balls (pills) or strings of rubber
in the belt grooves caused by the accumulation of
rubber dust.
Diagnostic Aids
Vibration from the engine may cause a body component or other parts to emit a rumbling noise.
The drive belt may have a condition that cannot be seen or felt. Sometimes the replacement of the belt may be the only
way to confirm the belt is faulty.
If the drive belt has been replaced and the diagnostic table completed, but the rumble is still present only when the drive
belt is installed, an accessory drive component such as the A/C compressor may be the cause. Varying the load to each
accessory drive component in turn, should help isolate which component is causing the noise.
Test Description
The numbers below refer to steps in the diagnostic table.
2 Confirms the symptom exists at the time of diagnosis. Other vehicle components may be causing the noise.
3 Confirms the accessory drive belt is the cause of the noise. Drive belt rumbling is often confused with an internal engine noise due to the similarity in the description. Removing the drive belt and operating the engine briefly will
confirm whether or not the noise is related to the drive belt.
CAUTION
When running the engine with the accessory
drive belt removed, the coolant pump will not
be operating and the engine may overheat if
left unsupervised even for a short period.
NOTE
There may also be a number of DTCs set when
running the engine with the accessory drive belt
removed.
4 Inspecting the drive belt is to ensure that it is not causing the noise. Small cracks across the ribs of the drive belt will not cause the noise and are not justification alone to replace the belt. Belt separation can be identified by the
ply of the belt separating and may be seen at the edge of the belt or felt as lumps under the belt.
5 Small amounts of pilling is a normal condition and is deemed acceptable. W hen the pilling is severe (33% of the belt groove depth), the belt does not have a smooth surface to run on and should be replaced.
Diagnostic Table
Step Action Yes No
1 Did you review the information provided in 2.2 Symptoms, and
perform the required inspections. Go to Step 2 Go to 2.2
Symptoms
2 Confirm the customer complaint. Is there a rumbling noise? Go to Step 3 Refer to Diagnostic
Aids in this Section
3 1 Remove the drive belt, refer to 3.5 Accessory Drive Belt.
2 Operate the engine for no more than 40 seconds.
Does the rumbling noise still exist? Accessory drive
system OK
Go to 2.2
Symptoms,
and restart the diagnosis Go to Step 4
4 Inspect the accessory drive belt for damage, separation or sections of missing ribs.
Did you find any damaged, separated or missing ribs? Go to Step 7 Go to Step 5
5 Inspect the accessory drive belt for severe pilling (exceeding 33% of the belt groove depth).
Did you find sever pilling? Go to Step 6 Go to Step 5

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ISUZU KB P190 2007

Engine Mechanical – V6 Page 6A1–49

Step Action Yes No
6 Clean the drive belt using a suitable wire brush and reinstall to the
engine, refer to 3.5 Accessory Drive Belt.
Did you complete the repairs? Go to Step 8 —
7 Install a new accessory drive belt, refer to 3.5 Accessory Drive Belt.
Did you replace the accessory drive belt? Go to Step 8
—
8 If required, reinstall the accessory drive belt and operate the system to
confirm the repair.
Did you correct the rumbling noise? Accessory drive
system OK Refer to Diagnostic
Aids in this Section
Drive Belt Vibration
Definition
Accessory drive belt vibration can be defined as a drive belt that jumps, shakes or rattles. Accessory drive belt vibration
is usually indicated by one of the following:
• the vibration is engine speed related, or
• the vibration is sensitive to accessory drive system load.
Diagnostic Aids
The accessory drive components such as the A/C compressor or generator can have an affect on engine vibration.
To aid in locating which component is causing the vibration, vary the load to each accessory drive component in turn and
note the effect it has on the vibration if any.
Test Description
The numbers below refer to steps in the diagnostic table.
2 Confirms the symptom exists at the time of diagnosis. Other vehicle components may be causing the noise.
3 Confirms the accessory drive belt is the cause of the noise. Drive belt rumbling is often confused with an internal engine noise due to the similarity in the description. Removing the drive belt and operating the engine briefly will
confirm whether or not the noise is related to the drive belt.
CAUTION
When running the engine with the accessory
drive belt removed, the coolant pump will not
be operating and the engine may overheat if
left unsupervised even for a short period.
NOTE
There may also be a number of DTCs set when
running the engine with the accessory drive belt
removed.
4 The drive belt may cause a vibration. Inspecting the drive belt is considerably easier while the drive belt is removed.
6 Inspecting the fasteners can eliminate the possibility that an incorrect fastener has been installed.
8 This step should only be performed if the coolant pump is driven by the drive belt. Inspect the coolant pump for a bent shaft. Also inspect the coolant pump bearings for smooth operation and excessive play. Compare the coolant
pump with a known good pump.
9 Accessory drive component brackets that are bent, cracked or loose may put extra strain on the accessory component causing it to vibrate.

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ISUZU KB P190 2007

Engine Mechanical – V6 Page 6A1–50

Diagnostic Table
Step Action Yes No
1 Did you review the information provided in 2.2 Symptoms, and
perform the required inspections. Go to Step 2 Go to 2.2
Symptoms
2 Confirm the customer complaint. Is there a rumbling noise? Go to Step 3 Refer to Diagnostic
Aids in this Section
3 1 Remove the drive belt, refer to 3.5 Accessory Drive Belt.
2 Operate the engine for no more than 40 seconds.
Does the vibration noise still exist? Accessory drive
system OK.
Go to 4.2
Symptoms, and
restart the diagnosis Go to Step 4
4 Inspect the accessory drive belt for damage, wear, debris build-up or
sections of missing ribs.
Did you find any damage, wear, debris build-up or missing ribs? Go to Step 5 Go to Step 6
5 Install a new accessory drive belt, refer to 3.5 Accessory Drive Belt.
Did you replace the accessory drive belt? Go to Step 10 —
6 Inspect for incorrect, loose, missing or damaged fasteners. Did you find any incorrect, loose, missing or damaged fasteners? Go to Step 7 Go to Step 8
7 Tighten any loose fasteners to the correct torque specification, refer to
6 Torque W rench Specifications.
Replace any incorrect or missing fasteners.
Did you complete the repairs? Go to Step 10 —
8 Inspect the coolant pump for a bent shaft, refer to 6B1 Engine Cooling – V6.
Did you find and repair a bent coolant pump shaft? Go to Step 10 Go to Step 9
9 Inspect for bent, cracked or damaged accessory drive component mounting brackets.
Did you find and repair any bent brackets? Go to Step 10 Refer to Diagnostic
Aids in this Section
10 If required, reinstall the accessory drive belt and operate the system to
confirm the repair.
Did you correct the vibration? Accessory drive
system OK Refer to Diagnostic
Aids in this Section
Drive Belt Falls Off
Definition
The drive belt falls off during normal operation or does not ride correctly on the accessory drive pulleys.
Diagnostic Aids
If the accessory drive belt repeatedly falls off the drive pulleys, this is most likely due to pulley misalignment.
An extra load that is quickly applied and released by an accessory drive component (e.g. A/C compressor) may cause
the accessory drive belt to fall off. In this circumstance, confirm the fault by operating the accessory drive components in
turn, noting which one caused the belt to fall off.
Lack of drive belt tension may also cause the belt to fall off the pulleys. Low drive belt tension could be caused by one of
the following:
• an incorrect drive belt length,
• a faulty drive belt tensioner, or
• a stretched or faulty drive belt.
Test Description
The numbers below refer to steps in the diagnostic table.
2 Confirms the condition of the drive belt. Damage may have occurred to the drive belt when it first fell off or it may have been damaged which caused the belt to fall off.
4 Misalignment of the pulleys may be caused by:

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ISUZU KB P190 2007

Engine Mechanical – V6 Page 6A1–51

• the incorrect installation or mounting of an accessory drive component,
• the incorrect installation of an accessory drive component pulley, or
• a damaged or bent accessory drive pulley.
Test for a misaligned pulley using a suitable straight edge in the pulley grooves across two or more pulleys. If a misaligned pulley is found, refer to the service information for the particular component, for the correct pulley
replacement procedures.
5 Inspecting the pulleys should include an inspection for dents or other damage that would prevent the drive belt from seating correctly in all of the pulley grooves or on the smooth surface of a pulley when the back side of the belt is
used.
6 Accessory drive component mounting brackets that are bent will cause the drive belt to fall off.
7 Inspection of the fasteners can eliminate the possibility that an incorrect fastener was installed. Missing, loose or incorrect fasteners may cause pulley misalignment from the fasteners moving under load. Over-tightening of the
fasteners may cause deflection of mounting brackets and result in misaligned accessory drive pulleys.
Diagnostic Table
Step Action Yes No
1 Did you review the information provided in 2.2 Symptoms, and
perform the required inspections. Go to Step 2 Go to 2.2
Symptoms
2 Inspect for a damaged accessory drive belt.
Did you find any damage on the drive belt? Go to Step 3 Go to Step 4
3 Install a new accessory drive belt, refer to 3.5 Accessory Drive Belt.
Does the drive belt continue to fall off? Go to Step 4 Go to Step 12
4 Inspect the accessory drive system pulleys for misalignment
Did you find and repair any misaligned drive system pulleys? Go to Step 12 Go to Step 5
5 Inspect for a dented or cracked accessory drive system pulley. Did you find and repair any dented or cracked drive system? Go to Step 12 Go to Step 6
6 Inspect for bent accessory drive component mounting brackets.
Did you find and repair any bent mounting brackets? Go to Step 12 Go to Step 7
7 Inspect for incorrect, loose, missing or damaged fasteners. Did you find any incorrect, loose, missing or damaged fasteners? Go to Step 8 Go to Step 9
8 Tighten any loose fasteners to the correct torque specification, refer to 6 Torque W rench Specifications.
Replace any incorrect or missing fasteners.
Does the drive belt continue to fall off? Go to Step 9 Go to Step 12
9 Test the accessory drive belt tensioner for correct operation, refer to
Accessory Drive Belt Tensioner Diagnosis in this Section.
Did you accessory drive belt tensioner operate correctly? Go to Step 11 Go to Step 10
10 Replace the drive belt tensioner, refer to
3.7 Accessory Drive Belt Tensioner Assembly.
Does the drive belt continue to fall off? Go to Step 11 Go to Step 12
11 Inspect for a failed drive belt idler and drive belt tensioner bearings.
Did you find and repair any failed bearings? Go to Step 12 Refer to Diagnostic
Aids in this Section
12 If required, reinstall the accessory drive belt and operate the system to confirm the repair.
Does the drive belt continue to fall off? Go to Step 2 Accessory drive
system OK
Drive Belt Excessive Wear
Definition
Excessive wear can be defined as wear at the outside ribs of the drive belt (frayed edges), usually caused by an
incorrectly installed drive belt

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ISUZU KB P190 2007

Engine Mechanical – V6 Page 6A1–52

Diagnostic Aids
Excessive wear of a drive belt is usually caused by an incorrect installation or an incorrect drive belt fitted. Minor pulley
misalignment will not cause excessive wear, but will cause the drive belt to fall off. Major pulley misalignment may cause
excessive wear, but would also result in the drive belt falling off.
Test Description
The numbers below refer to steps in the diagnostic table.
2 Confirms the drive belt is correctly installed onto all of the accessory drive system pulleys. W ear on the drive belt may be caused by incorrectly positioning the drive belt by one or more grooves to a particular pulley.
3 The installation of the drive belt that is the incorrect width will cause wear on the drive belt. The drive belt ribs should match all the grooves on all the pulleys in the accessory drive system.
4 Confirms the drive belt is not contacting any parts of the engine or body while the engine is running. There should be sufficient clearance when the accessory drive component loads varies. The drive belt should not come into
contact with any engine or body parts.
Diagnostic Table
Step Action Yes No
1 Did you review the information provided in 2.2 Symptoms, and
perform the required inspections. Go to Step 2 Go to 2.2
Symptoms
2 Inspect the accessory drive belt for correct installation.
Is the drive belt installed correctly? Go to Step 5 Go to Step 3
3 Ensure that the drive belt is the correct one for the application. Is the correct drive belt installed? Go to Step 5 Go to Step 4
4 Is the drive belt contacting any engine or body components with the engine running? Go to Step 6 Refer to Diagnostic
Aids in this Section
5 Install a new accessory drive belt, refer to 3.5 Accessory Drive Belt.
Did you replace the accessory drive belt? Go to Step 6 —
6 If required, reinstall the accessory drive belt and operate the system to confirm the repair.
Did you correct the excessive wear? Accessory drive
system OK Go to Step 2
Accessory Drive Belt Tensioner Diagnosis
Diagnostic Table
Step Action Yes No
1 1 Remove the accessory drive belt.
2 Inspect the drive belt tensioner pulley.
Is the drive belt tensioner pulley loose or misaligned? Go to Step 4 Go to Step 2
2 Rotate the drive belt tensioner.
Does the drive belt tensioner rotate freely, without any unusual
resistance or binding? Go to Step 3 Go to Step 4
3 1 Using a suitable torque wrench, measure the torque required to
lift the drive belt tensioner off the stop.
2 Using a known good tensioner, measure the torque required to lift the drive belt tensioner off the stop.
Is the first torque reading within 10% of the second reading?
Accessory drive belt tensioner OK Go to Step 4
4 Replace the drive belt tensioner, refer to
3.7 Accessory Drive Belt Tensioner Assembly.
Is the repair complete?
Accessory drive belt tensioner OK —

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ISUZU KB P190 2007