01–01 Engine-Support
Fasteners Checking
(Noise Emission
Control)
Check the front and the rear engine-support fasten-
ers for tightness. See
. See Group 01 of the
School Bus Chassis Workshop Manual
for specifica-
tions.
NOTE: At engine overhaul, and whenever the
engine has been removed, inspect the lower
and the upper isolators and replace them if they
are worn. See
, Refs. 1 and 6. See Sec-
tion 01.02 of the
School Bus Chassis Workshop
Manual for procedures.
01–02 Engine Drive Belt
Inspecting
WARNING
The engine and the belt must be cool before you
check the belt. Handling a hot belt can cause per-
sonal injury.
Worn or loose drive belts may cause premature
bearing failure or engine overheating. Excessive ten-
sion, or too little tension on the belt may result in ex-
cessive and premature belt wear. Poly-V belts, or
serpentine belts, are retained by a belt tensioner that
requires no tension adjustment. Replace the engine
drive belt if any conditions described in the visual
description are found. V-belts are installed as indi-
vidual belts, and as matched sets. When replacing a
matched set of belts, always replace both belts at the
same time. Matched belts must be from the same
manufacturer. To inspect a belt, gently twist the belt
to view the belt sidewalls and bottom. Visually in-
spect all drive belts for the following conditions, then
perform the belt tension inspection.
Visual Inspection
1.
Inspect the belt for glazing. See
, Ref. A.
Glazing is represented by shiny sidewalls, and is
caused by friction created when a loose belt slips
in the pulleys. It can also be caused by oil or
grease contamination on the pulleys.
2.
Check the belt for ply separation. See
Ref. B. Oil, grease, or belt dressing can cause
the belt to fall apart in layers. Repair any oil or
coolant leaks that are affecting the belts before
replacing the drive belts. Do not use belt dress-
ing on any belt.
3.
Check the belt for a jagged or streaked sidewall.
See
, Ref. C. Jagged or streaked sidewalls
are the result of foreign objects, such as sand or
gravel in the pulley, or a rough pulley surface.
4.
Check for tensile breaks (breaks in the cord
body). See
, Ref. D. Cuts in a belt are usu-
ally caused by foreign objects in the pulley, or by
prying or forcing the belt during removal or instal-
lation.
5.
Check for uneven ribs on serpentine (poly-V)
belts. See
, Ref. E. Foreign objects in the
pulley will erode the undercord ribs, causing the
belt to lose its gripping power.
6.
Check the drive belts for cracks. See
, Ref.
F. Small irregular cracks are usually the signs of
an old belt.
7.
Inspect the pulleys for excessive play or wobble.
Excessive play or wobble indicates a failure of
the pulley bearing. Check for belt squealing or
squeaking. Replace the bearings as necessary.
f220047a
1
2
3
4
5
6
2
10/05/94
1.
Lower Isolator
2.
Engine Support
Washer
3.
Capscrew
4.
Hexnut
5.
Engine Mount
6.
Upper Isolator
Fig. 1, Rear Engine Mount
Engine
01
School Bus Chassis Maintenance Manual, June 2003
01/1
