Air systems
Arguably one of the most important systems on a
heavy duty vehicle is the compressed air system.
On modern vehicles, multiple components may
rely on the air system: braking, suspension,
automated manual transmissions (AMT) and
even emissions systems. Because these critical
components require air, it is imperative that the
air system be kept in proper working condition
at all times.
Air systems: Problem
Excessive moisture in the air system can cause
issues at any time of year, but it is especially detrimental
in sub-freezing temperatures.
“Any moisture in the system when we get into
sub-freezing temperatures can cause brake line
freeze-up, valve freeze-up,” says Rich Nagel, director
of marketing and customer solutions at Bendix
12 Fleet Maintenance | October 2018
Charging. “Increasingly, air is used in pneumatic
automation, so you could have issues with automated
manual transmissions, emission controls,
all these things that run off of compressed air.”
If an air brake system freezes up, it can render
the vehicle inoperable and leave the driver
stranded in potentially unsafe conditions. Th e
only OEM-approved option to rectify the situation
is to tow the vehicle to a location where it
can be placed in a heated maintenance bay to
thaw, which can be very expensive and cause
increased downtime.
Th
ere are brake system deicer
additives available, but manufacturers
typically do not recommend
their use because they may
damage brake valves and other
system components. However,
when faced with extended downtime
and towing costs, fl eets may
choose to use them as a quick fi x.
Tim Hale, air system product
manager at Meritor, confi rms
that deicing compounds used
in extreme circumstances
should be used sparingly,
and that the amount and
application area of these
substances should be recorded due to
the potential to cause leaks or corrosion
of internal components.
“If you’re going to use a brake system
deicing additive, as part of your preventative
maintenance you may want to look at replacing
some of the products where you had issues,”
Nagel adds. “Th ose deicing compounds can
damage seals and they can do a lot of damage
to the brake valve.”
» The air dryer is located between the air
compressor and the rest of the air system. It
uses replaceable cartridges containing desiccant
material, which attracts and traps moisture
before it can reach the rest of the system.
Photo courtesy of Meritor
» Some engines can lose gallons of glycol in a year, so freeze levels must be
checked during a vehicle’s scheduled PM, especially before winter.
Photo courtesy of TravelCenters of America
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» To prevent fuel gelling, fleets should use
proper additives with every fill-up during months
when the weather has a potential to turn cold.
Photo courtesy of Penray
Fleets should be
sure to implement a
winterization plan to
prepare components
for cold weather.