GMC 2003 GMT560 T-Series Owner's Manual page 254

(31) = Check EGR system as described in the service
manual. See Service Publications Ordering Information
on page 7-6 .
(32) = 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.
(35) = Drain, flush and refill cooling system. See Part C:
Recommended Fluids and Lubricants on page 6-27
for what to use. Inspect hoses. Clean radiator,
condenser, pressure cap and neck. Pressure test
cooling system and pressure cap.
(37) = Rear axle service: Change the lubricant. See
Part C: Recommended Fluids and Lubricants on
page 6-27 .
(38) = Front axle service: Re-pack upper kingpin roller
bearing.
6-20
(39) = 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.