Suzuki XL7 2007 Service Manual page 378

1D-38 Engine Mechanical:
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.
Step
CAUTION
!
Refer to "Belt Dressing Notice: ".
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
– A damaged 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.
Did you review the Drive Belt Symptom operation and perform
1
the necessary inspections?
Verify that there is a rumbling noise or that the vibration is
2 engine related.
Does the engine make the rumbling noise or vibration?
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.
Action Yes
Go to "Symptoms -
Go to Step 2
Engine Mechanical"
Go to Step 3 Go to Diagnostic Aids
No