Diagnostic Information
If the accessory drive belt keeps slipping off the drive pulleys, it is most likely due to a misaligned pulley.
Rapid application and release of additional load by the accessory drive component (e.g. air conditioner compressor) may cause the accessory drive belt to slip. In this case, troubleshoot by operating the accessory drive components in turn, noting which one is causing the belt to slip.
Insufficient drive belt tension can also cause the belt to slip off the pulleys. Weak drive belt tension can be caused by one of the following reasons:
- incorrect length of the drive belt;
- defective drive belt tensioner or
- stretched or broken drive belt.
Description of the test
The item numbers below are the step numbers in the diagnostic table.
- Confirms the condition of the drive belt. Damage to the drive belt may have occurred when it first slipped, or damage to the drive belt may have caused it to slip.
- Skewed pulleys can be caused by the following reasons:
- improper installation or fastening of the accessory drive component;
- improper installation of the accessory drive component pulley or
- damage or bending of the drive pulley of the units.
- Inspection of the pulleys should include checking for dents or other damage that would prevent the drive belt from properly seating in all pulley grooves or on the smooth surface of the pulley when the reverse side of the belt is used.
- Bent accessory drive component mounting brackets can cause the drive belt to slip.
- Visual inspection of fasteners can eliminate the possibility that the wrong fastener was installed. Missing, loose, or incorrect fasteners can cause pulley misalignment due to fastener movement under load. Overtightening fasteners can cause deflection of the mounting brackets and misalignment of the accessory drive pulleys.
Check the alignment of the pulleys on the plane by applying a suitable ruler to the grooves of two or three pulleys. If a misaligned pulley is detected, refer to the specific component's service information for the correct pulley replacement procedure.
Diagnostic table
Definition: The drive belt slips under normal operating conditions or does not move correctly on the accessory drive pulleys.
| Step | Operation | Values | Yes | No |
| 1 |
Have you reviewed the information in the section "Symptoms", and performed the required checks?
|
-
|
Go to operation 2
|
Go to item Symptoms
|
| 2 |
Inspect the accessory drive belt for damage.
Is there damage to the drive belt?
|
-
|
Go to operation 3
|
Go to operation 4
|
| 3 |
Install a new accessory drive belt, see Section 1B, Engine Mechanical - 2.0 Diesel.
Does the drive belt keep slipping?
|
-
|
Go to operation 4
|
Go to operation 12
|
| 4 |
Check alignment of accessory drive system pulleys.
Have misaligned accessory drive system pulleys been detected and corrected?
|
-
|
Go to operation 12
|
Go to operation 5
|
| 5 |
Inspect the accessory drive system pulley for dents or cracks.
Have dents or cracks in the drive system been found and repaired?
|
-
|
Go to operation 12
|
Go to operation 6
|
| 6 |
Inspect the accessory drive component mounting brackets for bends.
Are bends in the mounting brackets found and repaired?
|
-
|
Go to operation 12
|
Jump to Operation 7
|
| 7 |
Inspect for correct installation, looseness, missing or damaged fasteners.
Are the wrong, loose, missing or damaged fasteners found?
|
-
|
Jump to operation 8
|
Go to operation 9
|
| 8 |
Tighten all loose fasteners to the correct torque to specifications.
Replace any incorrect or missing fasteners.
Does the drive belt keep slipping?
|
-
|
Go to operation 9
|
Go to operation 12
|
| 9 |
Check the correct operation of the accessory drive belt tensioner, see Section 1B, Engine Mechanical - 2.0 Diesel.
Is the accessory drive belt tensioner functioning correctly?
|
-
|
Go to operation 11
|
Jump to operation 10
|
| 10 |
Replace drive belt tensioner, see Section 1B, Engine Mechanical - 2.0 Diesel.
Does the drive belt keep slipping?
|
-
|
Go to operation 11
|
Go to operation 12
|
| 11 |
Visually inspect for defective idler pulley bearings and drive belt tensioner.
Have bearing failures been found and repaired?
|
-
|
Go to operation 12
|
See diagnostic advice in this section
|
| 12 |
If required, reinstall the accessory drive belt and operate the system to confirm repair is complete.
Does the drive belt keep slipping?
|
-
|
Go to operation 2
|
The drive system of the aggregates is in order
|