Unloader Installation; Testing The Rebuilt Compressor; Installing The Compressor - BENDIX BA-921 COMPRESSOR-STD-CLOSED ROOM Service Data Sheet

4. Install the cooling plate onto valve plate assembly by
lining up the alignment bushings on the cooling plate
over the oversized countersunk holes of the valve plate
assembly. Again, when properly installed, the outline
of the cooling plate matches the outline of the valve
plate.
5. Position and install the cylinder head over the alignment
bushings protruding from the cooling plate. When
properly installed, the outline of the cylinder head
assembly will match the outline of the cooling plate and
valve plate assembly.
Note: The alignment bushings will only fi t into two of the
cylinder head bolt holes.
6. Install the 6 hex head cylinder head bolts and washers
and snug them (fi nger tight), then torque the bolts in
the sequence specifi ed in Figure 18.
PART TWO: UNLOADER INSTALLATION
These instructions apply to both the Standard and
Closed Room Compressors.
7. Apply a coating of the lubricant provided in the unloader
kit into the unloader bore (both diameters). Apply
additional lubricant to the three o-ring grooves on the
unloader piston (10). Note that the o-ring (7) installs
inside the top of the unloader piston. Install the three
o-rings (7, 9, 11) into the appropriate o-ring grooves on
the unloader piston (10). Apply another coating of the
lubricant onto the exposed o-ring surfaces and onto
the large diameter of the balance piston (6). Install
the unloader piston with the pre-installed o-rings into
the cylinder head unloader bore making certain not to
damage them in the process.
8. Install the balance piston spring (8) in the unloader
piston.
9. Apply a coating of lubricant to the largest diameter of
the balance piston. Install the small diameter end of
the balance piston through the center of the spring.
10. Install the unloader cover gasket (5) on the cylinder
head making certain both screw holes align.
11. Position the unloader cover (4) on top of the balance
piston making certain the stamped logo is visible.
12. Press and hold the unloader cover in place on the
cylinder head, place the spray shield (3) (Standard
Compressors only) over the outboard hole (in order to
cover the vent slot in the unloader cap). Install both
unloader cover cap screws (2). Torque the cover cap
screws (2) to 62 to 71 inch pounds (7-8 N•m).

INSTALLING THE COMPRESSOR

1. Install the appropriate gasket or o-ring on the front
fl ange of the compressor. Make certain oil supply or
return holes in the gasket are properly aligned with the
compressor and engine. On the Detroit Diesel S60
engine installations, an additional o-ring is required to
seal the oil feed passageway between the compressor
and engine gear case cover. Gasket sealants are
not recommended. Secure the compressor on the
engine and tighten the mounting bolts per Engine
Manufacturers recommended torque requirements.
2. Install any supporting brackets on the compressor in the
same position(s) noted and marked during removal. If
a rear support bracket was on the original installation,
hand tighten the bolts on both ends before torquing the
bolts. Note: It is important that the rear support bracket
is fl ush to both surfaces before the bolts are torqued.
3. Inspect all air, oil, and coolant lines and fi ttings before
reconnecting them to the compressor. Make certain
o-ring seals are in good or new condition, the threads
are clean and the fi ttings are free of corrosion. Replace
as necessary.
4. Install the discharge, inlet, coolant and governor
adapter fi ttings, if applicable, in the same position on
the compressor noted and marked during disassembly.
See the Torque Specifi cations for various fi tting sizes
and types of thread at the rear of this manual. Tighten
all hose clamps.
5. Before returning the vehicle to service, perform
the Operation and Leakage Tests specifi ed in this
manual. Pay particular attention to all lines and hoses
disconnected during the maintenance and check for
air, oil, and coolant leaks at compressor connections.
Also check for noisy operation.

TESTING THE REBUILT COMPRESSOR

In order to properly test a compressor under operating
conditions, a test rack for correct mounting, cooling,
lubricating, and driving the compressor is necessary. Such
tests are not compulsory if the unit has been carefully rebuilt
by an experienced person. A compressor effi ciency or
build-up test can be run which is not too diffi cult. An engine
lubricated compressor must be connected to an oil supply
line of at least 15 psi pressure during the test and an oil
return line must be installed to keep the crankcase drained.
Connect to the compressor discharge port, a reservoir with
a volume of 1500 cubic inches, including the volume of the
connecting line. With the compressor operating at 2100
RPM, the time required to raise the reservoir(s) pressure
from 85 psi to 100 psi should not exceed 5 seconds. During
this test, the compressor should be checked for gasket
leakage and noisy operation, as well as unloader operation
and leakage. If the compressor functions as indicated,
reinstall on the vehicle connecting all lines as marked in
the disassembly procedure.
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