GMC 2010 T-Series Owner's Manual page 259

(21) = Check the fuel tank, fuel cap, and fuel lines for
damage which could cause leakage. Inspect fuel cap
for correct sealing ability and any indications of
damage. Check fuel cap gasket for even filler neck
imprint. Replace parts as needed.
(22) = Inspect Electronic Vacuum Regulator Valve
(EVRV) filter for excessive contamination or plugging.
If needed, clean filter with solution of soap and water,
let dry and install.
(23) = Drain, flush, and refill cooling system. This
service can be complex; you should have your dealer/
retailer perform this service. See Part C: Recommended
Fluids and Lubricants on page 6 28 for what to use.
Inspect hoses. Clean radiator, condenser, pressure cap,
and neck. Pressure test cooling system and
pressure cap.
(24) = Rear axle service: Change the lubricant. See
Part C: Recommended Fluids and Lubricants on
page 6 28.
(25) = Front axle service: Re-pack upper kingpin roller
bearing.
(26) = Air brake service:
Inspect brake lines and hoses for proper hook-up,
binding, leaks, cracks, chafing, etc. Inspect drum
brake linings for wear or cracks. Inspect other
brake parts at each wheel, including drums, wheel
cylinders and piston heat shields, boots and wheel
speed sensor wiring. Check brake pedal for
excessive free play or travel (or every 6 months,
whichever occurs first) and have serviced if
needed. Check brakes more often if driving habits
and conditions result in frequent braking. Replace
air dryer cartridge only if excessive oil or moisture
is present. A small amount of oil in the system is
normal and should not be considered as a reason
to replace the cartridge.
Test air lines for leaks; tighten as needed. Replace
compressor filter.
Inspect air parking brake chamber for leaks and
damage. Inspect lines and hoses for leaks, cracks,
chafing, etc. Also check all attachments for
tightness, wear, or damage. Note: The spring
brake section of the rear brake diaphragms are
non-serviceable.
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