Drive Belt Rumbling and Vibration Diagnosis
Diagnostic Aids
The accessory drive components can have an affect on engine
vibration. Vibration from the engine operating may cause a body
component or another part of the vehicle to make rumbling noise.
Vibration can be caused by, but not limited to the A/C system over
charged, the power steering system restricted or the incorrect
fluid, or an extra load on the generator. To help identify an
intermittent or an improper condition, vary the loads on the
accessory drive components.
The drive belt may have a rumbling condition that can not be
seen or felt. Sometimes replacing the drive belt may be the only
repair for the symptom.
If replacing the drive belt, completing the diagnostic table,
and the noise is only heard when the drive belts are installed,
there might be an accessory drive component with a failure. Varying
the load on the different accessory drive components may aid in
identifying which component is causing the rumbling noise.
Test Description
The numbers below refer to the step numbers on the diagnostic
table.
2 This test is to verify
that the symptom is present during diagnosing. Other vehicle
components may cause a similar symptom.
3 This test is to verify
that one of the drive belts is causing the rumbling noise or
vibration. Rumbling noise may be confused with an internal engine
noise due to the similarity in the description. Remove only one
drive belt at a time if the vehicle has multiple drive belts. When
removing the drive belts the water pump may not be operating and
the engine may overheat. Also DTCs may set when the engine is
operating with the drive belts removed.
4 Inspecting the drive
belts is to ensure that they are not causing the noise. Small
cracks across the ribs of the drive belt will not cause the noise.
Belt separation is identified by the plys of the belt separating
and may be seen at the edge of the belt our felt as a lump in the
belt.
5 Small amounts of
pilling is normal condition and acceptable. When the pilling is
severe the drive belt does not have a smooth surface for proper
operation.
9 Inspecting of the
fasteners can eliminate the possibility that the wrong bolt, nut,
spacer, or washer was installed.
11 This step should only
be performed if the water pump is driven by the drive belt. Inspect
the water pump shaft for being bent. Also inspect the water pump
bearings for smooth operation and excessive play. Compare the water
pump with a known good water pump.
12 Accessory drive
component brackets that are bent, cracked, or loose may put extra
strain on that accessory component causing it to vibrate.
Step
|
Action
|
Yes
|
No
|
|
Caution: Do
not use belt dressing on the drive belt. Belt dressing causes the
breakdown of the composition of the drive belt. Failure to follow
this recommendation will damage the drive belt. |
DEFINITION: The following items are indications of drive belt
rumbling:
| • |
A low pitch tapping, knocking, or thumping noise
heard at or just above idle. |
| • |
Heard once per revolution of the drive belt or a
pulley. |
| • |
Rumbling may be caused from: |
| -
|
Pilling, the accumulation of rubber dust that
forms small balls (pills) or strings in the drive belt pulley
groove |
| -
|
The separation of the drive belt |
DEFINITION: The following items are indications of drive belt
vibration:
| • |
The vibration is engine-speed related. |
| • |
The vibration may be sensitive to accessory
load. |
|
1
|
Did you review the Drive Belt Symptom operation and perform the
necessary inspections?
|
Go to Step 2
|
Go to
Symptoms - Engine Mechanical
|
2
|
Verify that there is a rumbling noise or that the vibration is
engine related.
Does the engine make the rumbling noise or vibration?
|
Go to Step 3
|
Go to Diagnostic Aids
|
3
|
|
1. |
Remove the drive belt. |
|
2. |
Operate the engine for no longer than 30-40
seconds. |
|
3. |
Repeat this test if necessary by removing the
remaining belts. |
Does the rumbling or vibration still exist?
|
Go to
Symptoms - Engine Mechanical
|
Go to Step 4
|
4
|
Inspect the drive belts for wear, damage, separation, sections of
missing ribs, and debris build-up.
Did you find any of these conditions?
|
Go to Step 7
|
Go to Step 5
|
5
|
Inspect for severe pilling of more than 1/3 of the drive belt
pulley grooves.
Did you find severe pilling?
|
Go to Step 6
|
Go to Step 7
|
6
|
|
1. |
Clean the drive belt pulleys with a suitable wire
brush. |
Did you correct the condition?
|
Go to Step 8
|
Go to Step 7
|
7
|
Install a new drive belt. Refer to
Generator, Air Conditioning Compressor, and Power Steering Pump
Belt Replacement .
Did you complete the replacement?
|
Go to Step 8
|
Go to Step 9
|
8
|
Operate the system in order to verify the repair.
Did you correct the condition?
|
System OK
|
Go to Step 9
|
9
|
Inspect for improper, loose or missing fasteners.
Did you find any of these conditions?
|
Go to Step 10
|
Go to Step 11
|
10
|
|
2. |
Replace improper or missing fasteners. |
Did you complete the repair?
|
Go to Step 13
|
Go to Step 11
|
11
|
Inspect for a bent water pump shaft. Refer to
Water Pump Replacement
Did you find and correct the condition?
|
Go to Step 13
|
Go to Step 12
|
12
|
Inspect for bent or cracked brackets.
Did you find and correct the condition?
|
Go to Step 13
|
Go to Diagnostic Aids
|
13
|
Operate the system in order to verify the repair.
Did you correct the condition?
|
System OK
|
Go to Step 3
|
|
| |
|
