Preparation For Disassembly - BENDIX BA-921 COMPRESSOR-STD-CLOSED ROOM Service Data Sheet

unless specifi cally stated and approved by the
vehicle and component manufacturer.
10. Prior to returning the vehicle to service, make
certain all components and systems are restored
to their proper operating condition.
11. For vehicles with Antilock Traction Control (ATC),
the ATC function must be disabled (ATC indicator
lamp should be ON) prior to performing any vehicle
maintenance where one or more wheels on a drive
axle are lifted off the ground and moving.
REMOVAL
In many instances it may not be necessary to remove the
compressor from the vehicle when installing the various
maintenance kits and service parts. The maintenance
technician must assess the installation and determine the
correct course of action.
These instructions are general and are intended to be
a guide. In some cases additional preparations and
precautions are necessary. In all cases follow the
instructions contained in the vehicle maintenance manual
in lieu of the instructions, precautions and procedures
presented in this manual.
1. Block the wheels of the vehicle and drain the air
pressure from all the reservoirs in the system.
2. Drain the engine cooling system and the cylinder head
of the compressor. Identify and disconnect all air, water
and oil lines leading to the compressor.
3. Remove as much road dirt and grease from the exterior
of the compressor as possible.
4. Remove the discharge and inlet fi ttings, if applicable,
and note their position on the compressor to aid in
reassembly.
Note: If a cylinder head maintenance kit is being
installed, stop here and proceed to PREPARATION FOR
DISASSEMBLY. If replacing the compressor continue.
5. Remove any supporting bracketing attached to the
compressor and note their positions on the compressor
to aid in reassembly.
6. Remove the front fl ange mounting bolts and remove
the compressor from the vehicle.
7. Inspect drive gear and associated drive parts for visible
wear or damage. If the compressor drive gear is worn
or damaged, the compressor must be replaced. Refer
the Engine Manufacturers service manual to address
the associated engine drive parts.
8. If the compressor is being replaced stop here and
proceed to "Installing the Compressor" at the end
of the assembly procedure. (Note: Replacement
compressors come with the drive gear pre-assembled
on the compressor.)

PREPARATION FOR DISASSEMBLY

Remove the balance of road dirt and grease from the
exterior of the compressor with a cleaning solvent. If a rear
end cover or end cover adapter is used on the compressor
being worked on, mark it in relation to the crankcase. It is
recommended, but not specifi cally necessary, to mark the
relationships of the cylinder head (13), cooling plate (15),
valve plate assembly (16), and crankcase (21).
A convenient method to indicate the above relationships
is to use a metal scribe to mark the parts with numbers or
lines. Do not use marking methods such as chalk that can
be wiped off or obliterated during rebuilding.
Prior to disassembly make certain that the appropriate
kits and or replacement parts are available. Refer to
Figure 15 for the standard compressor and Figure 16 for
the Closed-room compressor during the entire disassembly
and assembly procedure.
What follows is a description of a complete disassembly,
actual maintenance may only need to include portions of
these instructions.
CYLINDER HEAD
Section 1: Standard Compressor (refer to Figure 15)
1. Remove the discharge safety valve (12) from the
cylinder head (13).
2. To restrain the spring force exerted by balance piston
spring (8) of the unloader assembly, hold the unloader
cover (4) in place while removing the two unloader
cover cap screws (2) and spray shield (3). Carefully
release the hold on the unloader cover until the spring
force is relaxed, then remove the unloader cover.
3. Remove the unloader cover gasket (5).
4. Remove the balance piston (6), its spring (8) and the
unloader piston (10) along with its o-rings (7, 9 & 11)
from the cylinder head (13).
5. Remove the four hex head bolts (1) from the cylinder
head.
6. Gently tap the cylinder head, cooling plate (15) and
valve plate assembly (16) with a soft mallet to break
the gasket seal between the valve plate assembly and
the crankcase (21). Lift the cylinder head with cooling
plate and valve plate assembly off the crankcase.
7. Remove the metal inlet reed valve/gasket (17).
8. Gently tap the cylinder head, cooling plate and valve
plate assembly with a soft mallet to break the gasket
seals. Then separate the cylinder head from the cooling
plate (15) and valve plate assembly and remove the
two gaskets (14) between them.
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