Bendix Commercial Vehicle Systems BA-921 SMC COMPRESSOR - Manual (Page 8)

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9. Components with stripped threads or damaged
parts should be replaced rather than repaired. Do
not attempt repairs requiring machining or welding
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 Automatic 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 fi tting, if applicable, and note
their position on the compressor to aid in reassembly.
5. Remove any supporting bracketing attached to the
compressor and note their positions on the compressor
to aid in reassembly.
6. Remove the six mounting bolts that retain the
compressor to the side of the engine block. Note
the position of the six mounting bolts. Two of the six
bolts are shorter and must be installed in their original
locations. 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
to 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
Refer to Figure 9 during the entire disassembly and
assembly procedure.
Place a clean rag over the openings that expose the
gear and crankshaft / connecting rod assembly. No
contamination is permitted in these areas.
Remove the balance of the road dirt and grease from the
exterior of the compressor with a cleaning solvent. If the
rear end cover is being removed from the compressor
under repair, mark it, along with the two cap screws, in
relation to the crankcase. It is also recommended to mark
the relationship of the cylinder head, cooling plate, valve
plate assembly, and crankcase.
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 are available.
CYLINDER HEAD
1. Remove the discharge safety valve (9) from the cylinder
head.
2. To restrain the spring force exerted by the return spring
(3) of the unloader assembly, hold the unloader cover
in place while removing the two unloader cover cap
screws. 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 (4).
4. Remove the balance piston (5) with its o-ring (6); return
spring (3) and the unloader piston assembly (7) which
includes the unloader piston, two outer o-rings and two
guide bushings from the cylinder head.
5. Remove the six hex head bolts from the cylinder head.
Note: The fi ve hex bolts located towards the perimeter
of the cylinder head retain the cylinder head directly to
the crankcase. The single hex bolt in the center of the
cylinder head holds the cylinder head, cooling plate
and valve plate assembly together; independent of the
crankcase.
6. Gently tap the cylinder head, cooling plate and valve
plate assembly with a soft mallet to break the gasket
seal between the valve plate assembly and the
crankcase. Lift the cylinder head with cooling plate
and valve plate assembly off the crankcase.
7. Remove the metal inlet reed valve/gasket (1).