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Isuzu KB P190. Manual - part 632

Engine Mechanical – V6

Page 6A1–49

Step Action

Yes

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

—

Install a new accessory drive belt, refer to 3.5

Accessory

Drive Belt.

Did you replace the accessory drive belt?

Go to Step 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.

Confirms the symptom exists at the time of diagnosis. Other vehicle components may be causing the noise.

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.

N O T E

There may also be a number of DTCs set when
running the engine with the accessory drive belt
removed.

The drive belt may cause a vibration. Inspecting the drive belt is considerably easier while the drive belt is removed.

Inspecting the fasteners can eliminate the possibility that an incorrect fastener has been installed.

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.

Accessory drive component brackets that are bent, cracked or loose may put extra strain on the accessory
component causing it to vibrate.

Engine Mechanical – V6

Page 6A1–50

Diagnostic Table

Step Action

Yes

Did you review the information provided in 2.2

Symptoms, and

perform the required inspections.

Go to Step 2

Go to 2.2

Symptoms

Confirm the customer complaint. Is there a rumbling noise?

Go to Step 3

Refer to Diagnostic
Aids in this Section

Remove the drive belt, refer to 3.5

Accessory Drive Belt.

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

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

Install a new accessory drive belt, refer to 3.5

Accessory

Drive Belt.

Did you replace the accessory drive belt?

Go to Step 10

—

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

Tighten any loose fasteners to the correct torque specification, refer to
6

Torque Wrench Specifications.

Replace any incorrect or missing fasteners.

Did you complete the repairs?

Go to Step 10

—

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

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.

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.

Misalignment of the pulleys may be caused by:

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.

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.

Accessory drive component mounting brackets that are bent will cause the drive belt to fall off.

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

Did you review the information provided in 2.2

Symptoms, and

perform the required inspections.

Go to Step 2

Go to 2.2

Symptoms

Inspect for a damaged accessory drive belt.

Did you find any damage on the drive belt?

Go to Step 3

Go to Step 4

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

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

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

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

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

Tighten any loose fasteners to the correct torque specification, refer to
6

Torque Wrench Specifications.

Replace any incorrect or missing fasteners.

Does the drive belt continue to fall off?

Go to Step 9

Go to Step 12

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

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.

Confirms the drive belt is correctly installed onto all of the accessory drive system pulleys. Wear on the drive belt
may be caused by incorrectly positioning the drive belt by one or more grooves to a particular pulley.

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.

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

Did you review the information provided in 2.2

Symptoms, and

perform the required inspections.

Go to Step 2

Go to 2.2

Symptoms

Inspect the accessory drive belt for correct installation.

Is the drive belt installed correctly?

Go to Step 5

Go to Step 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

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

Install a new accessory drive belt, refer to 3.5

Accessory

Drive Belt.

Did you replace the accessory drive belt?

Go to Step 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

Remove the accessory drive belt.

Inspect the drive belt tensioner pulley.

Is the drive belt tensioner pulley loose or misaligned?

Go to Step 4

Go to Step 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

Using a suitable torque wrench, measure the torque required to
lift the drive belt tensioner off the stop.

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

Replace the drive belt tensioner, refer to

3.7

Accessory Drive Belt Tensioner Assembly.

Is the repair complete?

Accessory drive belt

tensioner OK

—

Content .. 630 631 632 633 ..