Technicians can use a thermal imaging camera to check temperature of the rotor after driving. In this
repair scenario, the left rear rotor (left) is almost 30 degrees hotter than the right rear brake rotor. There is
more heat on the left side than on the right due to the sticking brake.
60 PTEN DECEMBER 2017 www.VehicleServicePros.com
A scanned image of alignment information found
through iATN referencing the alignment procedure
for resetting the steering angle sensor.
show both signals matching exactly.
Our tests confirmed no problem with
the sensors.
3 THE REPAIR
We decided it best to bleed the
ABS system since the other shop said they
had replaced the module. ABS bleed procedures
are specific to the year, make and
model of the vehicle; there is not a “onesize
fits-all” process.
Due to this, it is best to return to your
vehicle information source for the procedure.
Remember we said we found a couple
of interesting items when we searched
the information database? What we found
was some specific information relating to
the bleed procedure reliant on the steering
angle sensor adjusted properly prior
to bleeding the system.
Like many newer vehicles, the steering
angle may cause brake pressure to be
applied to an individual wheel during a
traction control or ABS event in order to
maintain steering control. The angle of
the steering is one of the inputs into the
control module that determines whether
it is necessary to apply brake pressure to
maintain control.
The best way to reset the steering angle
sensor is to perform a four-wheel alignment
on the vehicle. After the alignment
is done, use your scan tool to complete a
steering angle reset. According to the specific
repair information on this vehicle, it
is required to set the alignment and perform
the reset when the steering wheel is
in the center of its tilt range. The reason
this needs to be done is as the steering
wheel tilts up or down, the wheel angle
changes slightly.
After the alignment and steering angle
reset, we manually bled the brakes using
the specified procedure along with our
scan tool.
Another piece of information we found
was, after bleeding the system the vehicle
manufacturer suggests driving the vehicle
safely while performing an ABS stop. You
should feel the brake pedal shudder and
the light come on during this process.
Once this is done, re-bleed the system
using the same procedure that was used to
originally bleed the system. To be honest,
we perform this ABS verification on every
vehicle we do any brake service on.
4 VERIFY THE REPAIR
In order to verify this repair, we
will need to drive it under the same conditions
that we used to cause the original
problem. In this case, it involved an extensive
test drive to see if there was any excess
heat or drag on the brake. After the test
drive, we checked each brake for consistent
heat using the thermal imaging camera.
This test showed even temperature
at every wheel. Next, we checked to see if
there was excess drag on any wheel. Each
wheel spun equally, indicating no issue.
Just to play it safe, we drove the vehicle
again and used the brakes excessively
to build a lot of heat. Additional testing
found no issues with either brake drag or
uneven heat.
The vehicle was returned to the other
shop with the instruction to have the
owner return for periodic checks over
a short period of time to make sure the
problem did not return. Checking with
the other shop confirmed the issue did
not return.
To sum it up, it is somewhat easy to
get complacent with seemingly routine
repairs. When problems occur, we rely
on our experience with similar faults to
correct issues when they occur, but there
are always going to be unique circumstances
that come up. Using every piece
of information at your disposal, keeping
an open mind, and going the extra mile
will almost always resolve anything that
comes up.
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