CAT: 8612 November 2019
Page 225
PREVENTIVE MAINTENANCE
ACCESSORY DRIVE BELTS
The reliability and service life of drive belts can be extended with proper
attention to installation, adjustment and maintenance. Neglect in these
matters could cause belt failure, resulting in potential hazards through
loss of the electrical or air system and possible engine damage due to
overheating.
SERPENTINE BELTS
A serpentine belt (also known as a Micro-V belt) is a single, continuous belt
used to drive multiple ancilliary devices on an automotive engine, such as
an alternator, power steering pump, water pump, A/C compressor. The
belt may also be guided by an idler pulley and/or a belt tensioner which
is usually spring loaded.
The drawback of this single belt is that if the belt breaks, the vehicle loses
all of its ancilliary devices; the belt typically gives ample visual warning of
impending failure, sometimes even totally shedding several grooves (ribs)
while still continuing to function normally.
Many vehicles now have serpentine drive belts this eliminates the need for
multiple V-belts. A spring-loaded pulley maintains tension on the serpentine
belt. This eliminates the need to re-tension the belt when it is replaced.
PACCAR MX-13 has two serpentine belts which eliminate the need for
multiple V-belts. A spring-loaded pulley on each serpentine belt maintains
constant belt tension during service and after belt replacement.
On PACCAR MX-13, the two belts are identified as 7PK and 9PK which
indicates the number of ribs on the belt. 9PK belt drives the water pump
and fan drive whilst 7PK drives the alternator and A/C compressor.
REPLACING 7PK & 9PK SERPENTINE BELTS
Switch off the ignition before disconnecting the battery clamp from the
negative pole.
NOTE: Non-observance of this waiting time results in clogging of the
AdBlue Lines.
Removing poly-V-belt 9PK - Engine Fan and Coolant Pump
1. Disconnect Battery Clamp, Negative Pole.
2. Move the tensioner against the spring force and lock it with a 4 to 5
mm thick locking pin or drill bit.
3. Remove the poly-V-belt from the pulleys.
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