Fleet Maintenance - 54

GUEST EDITORIAL
»»A tool like the Milton Industries Brake
Releaser can be used at tractor-trailer hookups, truck stops, or on the roadside as either
a pre-treatment or emergency air brake
releaser. It was invented by a lifelong driver
whose frozen trailer brakes caused him to
jackknife and nearly kill a state trooper.
Milton Industries

happens when the vehicle is parked, but it can
occur while driving down the road as well.

Moisture in trailer brakes
is not just a nuisance
Frozen brake lines can
mean costly repairs, delivery
delays, and safety issues.
Trailer brakes are one of the most neglected
service areas of combination tractor-trailers for
fleets. One reason for this is that fleet drivers
"drop and hook" trailers. In other words, they
are usually picking up a different trailer every
trip, so they never know the trailer's history.
The previous driver may not have been as diligent about daily air tank draining and may
have left moisture in the trailer's brake lines.

amber ABS alert light from illuminating. When
the ABS light is disabled, that means these trailers now function like they have standard brakes,
but still have ABS valves. If there's moisture in the
lines, those ABS valves can trap moisture, freeze
up, and cause brakes to not operate properly.
As stability control systems become standard
on all new trucks, managing moisture in trailer
brake lines becomes more important. If stability control is working properly, jackknives are
reduced by 66 percent and rollovers are reduced
by 68 percent, according to braking and safety
system supplier Bendix. But stability control
requires that the trailer's ABS be operational,
which U.S. DOT inspections have shown is often
not the case.

Managing moisture

Variables with system freezing

When I cover the air brake unit in my diesel technician training course, we walk out to the parking
lot and check truck air tanks. The students are
amazed at the liquid in both the primary and
secondary tanks. Over my years of doing this
survey, virtually every parked truck drained
some amount of water.
This accumulated moisture finds its way into
the trailer brake system and can cause various
issues, especially during winter months in cold
weather regions across the U.S. Ice crystals in a
trailer's air lines can lock up brakes creating a
cold morning annoyance, and in some cases, a
dangerous on-the-road jackknife.
Moisture can be a bigger issue if the trailer has
a disabled anti-lock braking system (ABS). For
example, the fuse may be removed to keep the

By Bill Peek

PRESIDENT, MPC PUBLISHING
Bill Peek is a heavy duty truck curriculum developer and
instructor. With a training career spanning more than
25 years, Peek has taught in 47 U.S. states and three
Canadian provinces. Peek created the Modern Diesel
Diagnostics course, including the unit on air brake systems with fellow trainer Doc Nall. Peek is president of MPC
Publishing, a print, video, and digital training provider. He
can be reached by phone at (219) 252-3148 or email at
mpcbill@gmail.com.

54 Fleet Maintenance | February 2020

Some believe moisture is not an issue because
modern trucks have air dryers. Let's look at
this from a technical perspective for a minute.
Coming out of the compressor, the air is extremely hot. The air has to be cooled down before it goes
through the dryer. There's a long line with a heat
dissipater that the air travels through to bring the
temperature down to below 212 degrees F before
it hits the dryer.
Next, the cooled air moves to the dryer, which
will get out most, but not all, of the moisture.
Even if the dryer air gets down to 180 degrees
F, once the truck is parked the airline will drop
to the ambient temperature. So, if it's 40 degrees
F outside, there will be moisture accumulation
simply because it's below the dew point. Is it
possible to ever get the air completely dry? Never.
Now there is moisture in the system. Here's
what can cause parts of the system to freeze:
While on the road, the driver applies and releases
the brakes, which causes an increase or decrease
in pressure. When the pressure drops, any moisture in the system condenses. Remember, the
higher the pressure, the higher the boiling point
of water. So, when the brakes are released, the
pressure quickly decreases from 125 psi toward
zero, creating moisture droplets that can find
their way into the valves. The colder the weather,
the faster these droplets can freeze. This usually

How to handle frozen
brake lines

There are a few ways drivers can choose to deal
with frozen brake lines in the field, including:
Torch it
Many veteran drivers have crawled under a
trailer with a torch and hammer to free up
frozen brakes. They heat up the valves to try to
melt the ice crystals, being careful not to melt
any hoses or ABS circuits. With a hammer, they
then tap the slack adjusters on the air chambers of each wheel and the brake shoes to see
if the brake has released. This method can lead
to damaged components.
Pull it
A driver may try to use brute force to drag a
frozen trailer hoping to jar loose ice crystals.
This works only if the brake lining is frozen to
the drum. The driver has no way to tell if it's the
lines or the drums that are frozen. This method
can cause damaged components and flat spots on
trailer tires.
Pour it
If using antifreeze or an air brake deicer, the
chemicals in the deicer melt the ice crystals in
the air line without requiring heat.
Pouring deicer directly into the brake line is
hard to do and it's difficult to tell if enough has
been added to be effective. Some brake system
manufacturers discourage using certain deicers or antifreeze solutions for fear that they
could remove some of the internal lubrication
from the seals, so be sure to use a solution
approved for the vehicle's brake system.
If these methods don't work, it means a costly
service call.
As a preventive measure, a tool like Milton
Industries' Brake Releaser can make it easier
to add an effective amount of deicing fluid to
the lines. To use, the driver detaches the gladhands and attaches the tool on the emergency
brake line, pours 6 oz to 8 oz of deicer into
the tool, and presses the red emergency brake
button in the cab. The Brake Releaser tool is
removed before vehicle operation. Milton
Industries says the entire process should take
about five minutes.
How drivers deal with frozen trailer brakes can
mean costly repairs, delivery delays, and safety
issues. Providing drivers the training and tools
they need to manage frozen brakes quickly and
safely can make all the difference.

Fleet Maintenance

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