Freightliner Business Class. Manual - part 9

Title of Maintenance Operation (MOP)

MOP Number

Engine Drive Belt Inspection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 01–02

Engine-Support Fasteners Checking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 01–01

Engine

Index, Alphabetical

Business Class Trucks Maintenance Manual, July 1999

01–01 Engine-Support

Fasteners Checking

Check the rear engine-support fasteners (

Fig. 1

, Ref.

4) for tightness. Tighten the 3/4-inch fasteners 215 to
265 lbf·ft (292 to 359 N·m).

Check the front engine-support fasteners for tight-
ness. Tighten the 5/8-inch fasteners 125 lbf·ft (170
N·m).

NOTE: At engine overhaul, and whenever the
engine has been removed, inspect the lower
and upper isolators (Refs. 1 and 6), and replace
them if they are worn. See Group 01 of the
Business Class

Trucks Service Manual for

procedures.

01–02 Engine Drive Belt

Inspection

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

Inspect the belt for glazing. See

Fig. 2

, 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.

Check the belt for ply separation. See

Fig. 2

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.

Check the belt for a jagged or streaked sidewall.
See

Fig. 2

, 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.

Check for tensile breaks (breaks in the cord
body). See

Fig. 2

, 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.

Check for uneven ribs on serpentine (poly-V)
belts. See

Fig. 2

, Ref. E. Foreign objects in the

pulley will erode the undercord ribs, causing the
belt to lose its gripping power.

Check the drive belts for cracks. See

Fig. 2

, Ref.

F. Small irregular cracks are usually the signs of
an old belt.

Visually 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.

NOTE: If it is difficult to distinguish the location
of a supposed bearing noise, obtain a stetho-
scope and place it on the component being
checked, not the pulley, to isolate the area from
outside interference.

f220047a

10/05/94

Lower Isolator

Engine Support
Washer

3/4 x 10 Capscrew

3/4 x 10 Hexnut

Engine Mount

Upper Isolator

Fig. 1, Engine Rear Mount

Engine

Business Class Trucks Maintenance Manual, July 1999

01/1

Inspect all pulleys for foreign objects, oil, or
grease in the grooves.

Belt Tension Inspection

NOTE: If engine drive belts require adjustment,
see Group 01 of the

Business Class

Trucks

Service Manual.

Threaded-Adjustment Type

Apply the parking brakes, and chock the tires to
prevent the vehicle from moving.

Install a belt tension gauge at the center of the
belt’s longest free-span. Check belt tension. See

Table 1

for belt tension specifications.

If belt tension is not correct, see Group 01 of the

Business Class

Trucks Service Manual

to adjust

belt tension.

Spring-Tension Type

On belts equipped with a spring tensioner, the belt
tension is automatically adjusted. Check that the ten-
sioner is holding tension on the belt by inserting the

end of a breaker bar in the 1/2-inch square hole on
the forward face of the tensioner, and rotating the
tensioner down, away from the belt. When the
breaker bar is slowly released, the tensioner should
return to its original position. If not, see Group 01 of
the

Business Class

Trucks Service Manual

for re-

placement instructions.

NOTE: The following engines are provided with
automatic drive belt tensioners: Caterpillar CFE,
Detroit Diesel Series 55, and Dodge Magnum.
The following engines, which appear in

Table 1

are provided with automatic tensioners for the
fan and alternator belts (and refrigerant com-
pressor for Caterpillar C10/C12): Caterpillar C10
and C12 and Cummins B and C Series.

Drive Belt Tensions

Engine

Component

Belt Tension

lbf (kg)

Cummins B and C Series

Refrigerant Compressor

100 (45)

Cummins M11

Alternator

105 (48)

Fan

160 (73)

Refrigerant Compressor

90 (41)

Detroit Diesel Series 50

Fan and Alternator

70 (32)

Refrigerant Compressor

95 (43)

Mercedes-Benz OM366LA

Fan and Alternator

160 (73)

Refrigerant Compressor

100 (45) or 140 (64)

Air Compressor

50 (23)

For a regular V-belt, tighten the belt to 100 lb (45 kg). For a Powerband

V-belt, tighten the belt to 140 lb (64 kg).

Table 1, Drive Belt Tensions

Engine

Business Class Trucks Maintenance Manual, July 1999

01/2

f150010a

11/21/94

A. Glazing
B. Separating Layers
C. Streaked Sidewalls

D. Tensile Break
E. Uneven Ribs
F.

Cracks

Fig. 2, Drive Belt Replacement Conditions

Engine

Business Class Trucks Maintenance Manual, July 1999

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