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For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2005 🢒 Isuzu MD F-Series 🢒 Engine 🢒 Engine Mechanical - 7.8L 🢒 Drive Belt Squeal Diagnosis

Diagnostic Aids

A loose or improper installation of a body component, a suspension component, or other items of the vehicle may cause the squeal noise.

If the noise is intermittent, verify the accessory drive components by varying their loads making sure they are operated to their maximum capacity. An overcharged A/C system or a generator failing are suggested items to inspect.

Test Description

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

  1. 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.

    2.

  2. The noise may be an internal engine noise. Removing the drive belt and operating the engine for a brief period will verify the squeal noise is the drive belt or an accessory drive component. When removing the drive belt the water pump will not be operating and the engine may overheat. Also DTCs may set when the engine is operating with the drive belt removed.

    3.

  3. This test is to verify that an accessory drive component does not have a seized bearing. With the belt removed test the bearings in the accessory drive components for turning smoothly. Also test the accessory drive components with the engine operating by varying the load on the components to verify that the components operate properly.

    4.

  4. 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.

    5.

  5. 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.

    6.

  6. This test is to verify that the pulleys are the correct diameter or width. Using a known good vehicle compare the pulley sizes.

Step

Action

Yes

No

Notice: Refer to Belt Dressing Notice in the Preface section.

DEFINITION: The following items are indications of drive belt squeal:

    • A loud screeching noise that is caused by a slipping drive belt (this is unusual for a drive belt with multiple ribs)
    • The noise occurs when a heavy load is applied to the drive belt, such as an air conditioning compressor engagement snapping the throttle, or slipping on a seized pulley or a faulty accessory drive component.

1

Verify that there is a squeal noise.

Does the engine make the squeal noise?

Go to Step 2

System OK

2

  1. Remove the drive belt. Refer to Drive Belt Replacement .
  2. Operate the engine for no longer than 30 to 40 seconds.

Does the noise still exist?

Go to Vibration Analysis - Engine in Vibration Diagnosis and Correction

Go to Step 3

3

Inspect for an accessory drive component seized bearing or a faulty accessory drive component.

Did you find and correct the condition?

Go to Step 7

Go to Step 4

4

Inspect for the correct drive belt length. Refer to Drive Belt Replacement .

Did you find and correct the condition?

Go to Step 7

Go to Step 5

5

Inspect for misalignment of a pulley.

Did you find and correct the condition?

Go to Step 7

Go to Step 6

6

Inspect for the correct pulley size.

Did you find and correct the condition?

Go to Step 7

Go to Step 2

7

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2