Inspection Of Parts; Cylinder Head, Cooling Plate/Valve Plate Assembly/Unloader Mechanism; Crankcase; Foot Pounds To Inch Pounds - BENDIX BA-921 COMPRESSOR-STD-CLOSED ROOM Service Data Sheet

plate assembly. They must be open and clear in both
assemblies. Make certain not to damage the head.
3. Remove rust and scale from the cooling cavities and
passages in the cylinder head, cooling plate and valve
plate assembly and use shop air to clear debris from
the passages.
4. Check the threads in all cylinder head ports for
galling (e.g. abrasion, chafi ng). Minor thread chasing
(damage) is permitted.
5. Make certain the unloader vent passage under the
unloader cover (4) in the head is open and free of
debris. NOTE: This only applies to the unloader cover
on the Standard Compressor.

INSPECTION OF PARTS

CYLINDER HEAD, COOLING PLATE, VALVE
PLATE ASSEMBLY AND UNLOADER
MECHANISM
1. Carefully inspect the head gasket surfaces on the
cylinder head (13) for deep gouges and nicks. Also,
inspect the cylinder head for any cracks or port thread
damage. If detected, the compressor must be replaced.
If large amounts of carbon build-up are present in
the discharge cavity such that it restricts the air fl ow
through the cylinder head, the compressor should be
replaced.
2. Carefully inspect both sides of the head gasket surfaces
on the cooling plate (15) for deep gouges and nicks.
Also, inspect the cooling plate for any cracks or other
damage. If found, the compressor must be replaced.
3. Carefully inspect the valve plate assembly (16) gasket
surfaces (both sides) for deep gouges and nicks. Pay
particular attention to the gasket surface. An inlet
reed valve/gasket (17) is used between the valve
plate assembly and crankcase. This gasket surface
must be smooth and free of all but the most minor
scratches. If excessive marring or gouging is detected,
the compressor must be replaced. If large amounts of
carbon build-up are present on the two main surfaces, in
the two discharge valve holes or between the discharge
valve and the discharge seat, the compressor should
be replaced.
4. If the unloader assembly has been removed from the
cylinder head, the unloader assembly must be serviced
using an unloader kit. (See Maintenance Kits, page
12.)
5. If large amounts of carbon build-up are present on the
unloader piston (10) seat or orifi ce or if the return spring
exhibits compression set, the unloader components
must be replaced with an unloader kit.
REAR END COVER (If Present)
Check for cracks and external damage. Check the
crankshaft rear bearing diameter in the rear end cover
(25) for excessive wear, fl at spots or galling. Check the
rear support bracket threaded holes and hydraulic pump
attachment threaded holes (if present) for thread damage.
Minor thread chasing is permitted but do not re-cut the
threads. If any of these conditions are found, replace the
compressor.

CRANKCASE

Check the cylinder head gasket surface on the deck (top)
of the crankcase (21) for nicks, gouges, and marring.
A metal gasket is used to seal the cylinder head to the
crankcase. This surface must be smooth and free of all but
the most minor scratching. If excessive marring or gouging
is detected, the compressor must be replaced.
ASSEMBLY
General Note: All torques specifi ed in this manual are
assembly torques and typically can be expected to fall off
after assembly is accomplished. Do not re-torque after
initial assembly torques fall unless instructed otherwise.
A compiled listing of torque specifi cations is presented on
page 18.
INCH POUNDS TO FOOT POUNDS
To convert inch pounds to foot pounds of torque, divide
inch pounds by 12.
Example: 12 Inch Pounds = 1 Foot Pound
12

FOOT POUNDS TO INCH POUNDS

To convert foot pounds to inch pounds of torque, multiply
foot pounds by 12.
Example: 1 Foot Pound x 12 = 12 Inch Pounds
CRANKCASE COVER
1. Position the crankcase cover gasket (27) on either the
crankcase or crankcase cover and install the crankcase
cover on the crankcase using the four cap screws.
"Snug" all four cap screws then torque to 62-71 inch
pounds (7-8 N•m) using a crossing pattern.
2. In the case of the Caterpillar C11 and C13 engine
application, the compressor utilizes an "oil jet" that
sprays oil under the piston for purposes of cooling.
This oil jet is part of a special crankcase cover that is
used strictly on the compressor for the C11 and C13
engine installation (See Figure 14). Refer to section
OPERATION – Lubrication for description of the system.
To re-assemble, follow the instructions below.
15