GMC 4000 Series Service Manual page 189

Sec. 5A
Page 182
HYDRAULIC BRAKES
Figure 2 1 — Power Cylinder Air Cleaner Installed (Conv.)
cleaner has become so laden with an accumulation
of dirt, that satisfactory cleaning cannot be done,
replace it with a new cleaner.
The air cleaner used on the conventional and
all Tilt-Cab Models is a plastic encased, synthetic
G M C S E R V I C E M A N U A L
Figure 2 2 — Pow er Cylinder A ir Cleaner (D a sh -M o u n te d Booster)
element type filter and cleaning is NOT recom ­
mended. When cleaner becomes so laden with dirt,
that tapping it against some solid surface (such as
a work bench) will not remove foreign matter, then
a new cleaner should be installed.
The air cleaner used with dash mountedpower
cylinders is an integral part of the assembly. This
air cleaner is a cylindrical piece of polyurethane
foam which is fastened on the power cylinder push
rod. This air cleaner can be removed from the
assem bly, cleaned,^and replaced.
LOCATION OF AIR CLEANERS
The air cleaner on the P4500 Model vehicles
is located on the dash panel in front of the driver's
seat and is readily accessible.
The air cleaner on "S" Models is located on
the fire wall under the dash on the driver's side.
The air cleaner on the conventional models is
located in the left rear corner of the cab, directly
behind the driver's seat. The air cleaner on the
Tilt-Cab models is located in front of the radiator
near the vacuum power cylinder and is accessible
by tilting cab forward. To remove cleaner from
conventional or tilt cab, unfasten nut and bolt hold­
ing cleaner to bracket and pull cleaner off air hose
(see fig. 21).
The air cleaner on models equipped with dash
mounted boosters is located in the booster hub on
the push rod. To remove this air cleaner it is nec­
essary to disconnect push rod from brake pedal
and remove push rod from booster assem bly. This
requires approximately 225 lbs. pulling force and
therefore some sort of leverage is needed. This
can be done without removing booster from the
vehicle. It must be done from inside the cab or
body. The nylon push rod retainer will be broken
upon removal, therefore a new retainer should be
available before removing push rod. Remove filter
from push rod, clean as directed in LUBRICATION
(SEC. 0) in this manual, and replace on push rod.
Reinstall push rod and connect to brake pedal.
Refer to figure 22 for illustration of this type of
filter.