Diagnostic information
If the accessory drive belt is constantly slipping off the drive pulleys, it is most likely due to a pulley being out of alignment.
Rapid application and release of additional load by the drive component of the aggregates (for example, an air conditioning compressor) may cause the accessory drive belt to slip. In this case, establish the fault by operating the accessory drive components one by one, 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 drive belt length;
- faulty drive belt tensioner or
- stretching or malfunction of the drive belt.
Description of the test
The item numbers below are the step numbers in the diagnostic chart.
- Confirms the condition of the drive belt. The drive belt may have been damaged when it first slipped, or the damage may have caused it to slip.
- The following reasons may cause the pulleys to become misaligned:
- incorrect installation or fastening of the drive component of the units;
- incorrect installation of the drive component pulley of the units or
- damage or bending of the drive pulley of the units.
- Inspection of pulleys should include checking for dents or other damage that would prevent the drive belt from seating properly in all pulley grooves or on the smooth surface of the pulley when the back side of the belt is used.
- Bent accessory drive component mounting brackets can cause the drive belt to slip.
- A visual inspection of the fasteners can eliminate the possibility that the wrong fasteners were installed. Missing, loose, or incorrect fasteners can cause pulley misalignment due to the fastener moving under load. Over-tightening the fasteners can cause the mounting brackets to deflect and cause the accessory drive pulleys to misalign.
Check the pulley alignment by placing a suitable straight edge across the grooves of two or three pulleys. If a pulley is found to be out of alignment, refer to the specific component service information for the correct pulley replacement procedure.
Diagnostic table
Definition: Drive belt slips under normal operating conditions or does not ride correctly on accessory drive pulleys.
| Step | Operation | Values | Yes | No |
| 1 |
Have you reviewed the information provided in the Symptoms section and performed the required checks?
|
-
|
Jump to operations 2
|
Go to item Symptoms
|
| 2 |
Inspect the accessory drive belt for damage.
Is there any damage found on the drive belt?
|
-
|
Jump to operations 3
|
Jump to operations 4
|
| 3 |
Install a new accessory drive belt, see. Section 1B, Engine Mechanical System - 2.0 Diesel.
Does the drive belt continue to slip?
|
-
|
Jump to operations 4
|
Jump to operations 12
|
| 4 |
Check the alignment of the drive system pulleys of the units along the plane.
Have the misalignments of the drive system pulleys been detected and corrected?
|
-
|
Jump to operations 12
|
Jump to operations 5
|
| 5 |
Inspect the drive pulley for dents or cracks.
Have any dents or cracks in the drive system been found and repaired?
|
-
|
Jump to operations 12
|
Jump to operations 6
|
| 6 |
Inspect the drive component mounting brackets for bends.
Have the bends in the mounting brackets been detected and corrected?
|
-
|
Jump to operations 12
|
Jump to operations 7
|
| 7 |
Inspect for correct installation, looseness, missing or damaged fasteners.
Are any incorrect, loose, missing or damaged fasteners found?
|
-
|
Jump to operations 8
|
Jump to operations 9
|
| 8 |
Tighten all loose fasteners to the correct torque according to specifications.
Replace all incorrect or missing fasteners.
Does the drive belt continue to slip?
|
-
|
Jump to operations 9
|
Jump to operations 12
|
| 9 |
Check the correct operation of the accessory drive belt tensioner, see. Section 1B, Engine Mechanical System - 2.0 Diesel.
Is the accessory drive belt tensioner functioning properly?
|
-
|
Jump to operations 11
|
Jump to operations 10
|
| 10 |
Replace the drive belt tensioner, see. Section 1B, Engine Mechanical System - 2.0 Diesel.
Does the drive belt continue to slip?
|
-
|
Jump to operations 11
|
Jump to operations 12
|
| 11 |
Visually check for faulty tension roller bearings and drive belt tensioner.
Bearing faults found and corrected?
|
-
|
Jump to operations 12
|
See diagnostic recommendations in this section
|
| 12 |
If required, reinstall the accessory drive belt and operate the system to confirm completion of the repair.
Does the drive belt continue to slip?
|
-
|
Jump to operations 2
|
The drive system of the units is in order
|