GMC T-Series 2007, Owner'S Manual, Page: 231 / 356

Air Dryer
If your vehicle has air brakes, it will have an air
dryer. This collects and removes dirt, moisture, or
other foreign matter from the air prior to entering
the brake system. The air dryer also serves as a
moisture ejector. It automatically ejects the
moisture when the compressor cycles. The integral
purge tank has a manual drain valve that must be
drained every day. See “Air Brake Systems” for the
manual drain procedure. The dryer is mounted on
the driver side frame rail.
The dryer has a filter that
you need to change at
intervals. See Scheduled
Maintenance on
page 295 for more
about servicing this filter.
Electric Air Compressor
Your vehicle may have an electric air compressor.
This compressor is used to run options that
require pressurized air, such as air horn, air
seat, exhaust restrictor, or an exhaust brake.
The air compressor is used when vehicles do
not have an air brake system.
The air supply for
this system must be
maintained by releasing
the drain valve to
eject any moisture
that could have built
up in the system.
It is recommended that this system be drained on
a weekly basis.
Clutch Pedal Free Travel
Normal clutch pedal free play is 1.5 to 2 inches
(38 to 51 mm) measured from the floorboard.
If the free play is less than 1.25 inches (32 mm),
adjustment is required.
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