TU-FLO 400, 500, 1000 AIR COMPRESSORS: Formerly SD-01-2
TU-FLO 400, 500, 1000 AIR COMPRESSORS: Formerly SD-01-2
SD-01-326
TU-FLO 400, 500, 1000 AIR COMPRESSORS *Formerly SD-01-2
TU-FLO 1000
1
main local global operation trouble-
menu search search shooting
DESCRIPTION AND OPERATION and they have no external moving parts. Both air and water
cooled type compressors are available. Various mounting
GENERAL and drive adaptations are used as required by different vehicle
The function of the air compressor is to build up and maintain engine designs (Fig. 4).
the air pressure required to operate air powered devices in
air brake or air auxiliary systems.
DESCRIPTION
Tu-Flo Type 400, 500, and 1000 compressors are single
stage, reciprocating piston type compressors. Tu-Flo 400
(Fig. 1) and 500 (Fig. 2) compressors have two cylinders
while the Tu-Flo 1000 (Fig. 3) is a V-type design having four
cylinders. The rated capacity of all Bendix compressors is
their piston displacement in cubic feet per minute when
operating at 1,250 RPM. The rated capacity of the Tu-Flo
400 compressor is 7-1/4 cubic feet per minute. The Tu-Flo
500 is rated at 12 cubic feet per minute and the Tu-Flo 1000
has a rating of 24 cubic feet per minute.
Tu-Flo type compressors have automatic type inlet valves.
Their unloading mechanisms are located in the cylinder block
OPERATION
GENERAL
All compressors run continuously while the engine is running,
but actual compression of air is controlled by a governor,
FIGURE 5 FIGURE 6 which stops or starts the compression of air by loading or
ENGINE LUBRICATED TYPE SELF-LUBRICATED TYPE unloading the compressor in conjunction with its unloading
mechanism. This is done when the air pressure in the system
had either die cast aluminum, cast ductile iron, or forged reaches the desired maximum or minimum pressures.
steel rods which were not rifle drilled but were drilled at the
top of the rod. The wrist pins and bushings are lubricated
by oil dripping from a drip-boss on the piston into a
catch-funnel at the top of the rod and through the drilled TO RESERVOIR
passage to the bushings and pins. (SEE FIG. 7) INLET VALVE
DISCHARGE
VALVE UNLOADER PLUNGER
PISTON
INTAKE
PISTON WRIST PIN WRIST PIN STRAINER
LOCK WIRE BUSHING
TO GOVERNOR
CAST IRON
WRIST PIN PISTON
STROKE
OIL STEEL INTAKE
PASSAGE CONNECTING FIGURE 9
ROD
OLD DESIGN
INTAKE AND COMPRESSION (Loaded)
CATCH FUNNEL During the down stroke of the piston, a slight vacuum created
above the piston causes the inlet valve to move off its seat.
WRIST PIN Atmospheric air is drawn in through the compressor intake,
BUSHING
DIE CAST by the open inlet valve, and on top of the piston (Fig. 9). As
PISTON the piston starts its upward stroke, the air that was drawn in
on the down stroke is being compressed. Now, air pressure
DIE CAST
CONNECTING ROD on top of the inlet valve plus the force of its spring, returns
NEW DESIGN the inlet valve to its seat. The piston continues the upward
stroke and compresses the air sufficiently to overcome the
FIGURE 7- PISTONS & CONNECTING RODS discharge valve spring and unseat the discharge valve. The
compressed air then flows by the open discharge valve, into
A nameplate is attached to the crankcase of all compressors.
the discharge line and on to the reservoirs (Fig. 10).
It shows the piece number, type and serial number (Fig. 8).
A nameplate with a black background denotes a new
compressor, whereas a nameplate with a red background
designates that the compressor is a factory reconditioned
unit. All compressors are identified by the piece number
TO RESERVOIR
which is the number to use when reference is made to a INLET VALVE
DISCHARGE
particular compressor. The type and serial number is VALVE UNLOADER PLUNGER
supplementary information.
PISTON INTAKE
STRAINER
TO GOVERNOR
STROKE
COMPRESSION
FIGURE 8 - COMPRESSOR NAMEPLATE FIGURE 10
3
main local global operation trouble-
menu search search shooting
As the piston reaches the top of its stroke and starts down,
the discharge valve spring returns the discharge valve to its
seat. This prevents the compressed air in the discharge
line from returning to the cylinder bore as the intake and
compression cycle is repeated.
NON-COMPRESSION (Unloaded)
When the air pressure in the reservoir reaches the high
pressure setting of the governor, the governor opens, allowing
air to pass from the reservoir through the governor and into
the cavity beneath the unloader pistons. This lifts the
unloader pistons and plungers. The plungers move up and FIGURE 12
hold the inlet valves off their seats (Fig. 11 ). OIL LEVEL - SELF-LUBRICATED COMPRESSOR
TO GOVERNOR
STROKE
UNLOADING
FIGURE 11
With the inlet valves held off their seats by the unloader
pistons and plungers, air is merely pumped back and forth
between the two cylinders. When air is used from the
reservoir and the pressure drops to the low pressure setting
of the governor, the governor closes, and in doing so,
exhausts the air from beneath the unloader pistons. The
unloader saddle spring forces the saddle, pistons and
plungers down and the inlet valves return to their seats.
Compression is then resumed. FIGURE 13 - POLYURETHANE SPONGE STRAINER
COOLING
Tu-Flo 400, 500 or 1000 compressors may be air-cooled or
water- cooled and in some instances will have air-cooled
blocks and water-cooled heads. The air-cooled versions
are easily recognized by the external fins. The water-cooled
versions are cooled by vehicle coolant.
PREVENTIVE MAINTENANCE
If the compressor is a self-lubricated type, its oil level should
be checked daily. The oil level should be kept between the
bottom of the dipstick threads and the bottom of the dipstick
(Fig. 12). Every 8,000 miles or 300 operating hours, the oil
should be drained and refilled with SAE 10-20-30.
FIGURE 14
DRY ELEMENT- PLEATED PAPER AIR STRAINER
4
main local global operation trouble-
menu search search shooting
7
main local global operation trouble-
menu search search shooting
INSPECTION OF PARTS
CYLINDER HEAD BODY
8
main local global operation trouble-
menu search search shooting
COMPRESSION
RINGS (2)
COMPRESSION
RINGS (2)
.0015
FIGURE 20 - MEASURING CYLINDER BORES .0030
CORRECT GAP
CLEARANCE WITH RING
IN CYLINDER
Clearance between cast iron pistons and cylinder bores
should be between 0.002 in. minimum and 0.004 in. .0035
.014
maximum (Fig. 20).
FIGURE 22 - TU-FLO 400 OLD STYLE
PISTONS
TU-FLO 500 & 1000 COMPRESSOR
Check pistons for scores, cracks or enlarged ring grooves; CORRECT GROOVE
replace pistons if any of these conditions are found. Measure CLEARANCE
NARROW
each piston with a micrometer in relation to the cylinder
WIDE
bore diameter to be sure the clearance is between 0.002 in.
minimum and 0.004 in. maximum. .0035 .002
.0035 .004
Check fit of wrist pins on pistons and connecting rod bushings. CORRECT GAP
Wrist pin should be a light press fit in pistons. If wrist pin is CLEARANCE WITH RING
IN CYLINDER
loose fit, the pin, piston, or both should be replaced. Check NARROW
fit of wrist pin in connecting rod bushing by rocking the piston. .0035 WIDE
This clearance should not exceed 0.0015 in. Replace wrist .014
pin bushings if excessive clearance is found. Wrist pin
bushings should be reamed after being pressed into FIGURE 23 - PISTON RING POSITIONS - GAPS AND
GROOVE CLEARANCE
connecting rods. Replace used wrist pin lock wires. Tu-Flo
400 compressors manufactured after September 1977 will
have Teflon plugs in each end of the wrist pins instead of the
lock wire. The Teflon plugs (pc. no. 292392) may be used CRANKSHAFT
instead of the lock wires on all compressors. See Fig. 21. Check crankshaft screw threads, keyways, tapered ends
PISTON RINGS and all machined and ground surfaces for wear, scores, or
damage. Crankshaft journals which are out of round more
Check fit of piston rings in piston ring grooves. Check ring
than 0.001 in. must be reground. Bearing inserts are available
gap with rings installed in cylinder bores. Refer to Fig. 23
in 0.010 in., 0.020 in., and 0.030 in. undersizes for reground
for correct gap and groove clearance.
crankshafts. Main bearing journals must be maintained so
All rings must be located in their proper ring grooves as bearings are snug fit. The oil seal ring groove or grooves in
shown. The rings can be identified by the width and should crankshafts fitted with oil seal rings must not be worn. The
be installed with the bevel or the pipmark (if any) toward the ring groove walls must have a good finish and they must be
top of the piston. This applies to Cast Iron Pistons (only as square. Check to be sure the oil passages are open and
shown above). clean through the crankshaft.
Die Cast Pistons use five (5) narrow rings.
9
main local global operation trouble-
menu search search shooting
CONNECTING ROD BEARINGS Leakage which will permit the formation of bubbles is
Check connecting rod bearings on crankshaft journals for permissible.
proper fit. Used bearing inserts should be replaced. If excessive leakage is found, leave the air pressure applied,
Connecting rod caps are not interchangeable. The locking and with the use of a fibre or hardwood dowel and hammer,
slots of the connecting rod and cap should be positioned tap the discharge valves off their seats several times. This
adjacent to each other. will help the valves to seat and should reduce any leakage.
Clearance between the connecting rod journal and the With the air pressure still applied at the discharge port of
connecting rod bearing must not be less than 0.0003 in. or the cylinder head, check for leakage at the discharge valve
more than 0.0021 in. after rebuilding. cap nuts. No leakage is permissible.
MAIN BEARINGS INLET VALVES AND SEATS
Check for wear or flat spots; if found, bearings should be If inlet valve seats show sign of slight nicks or scratches,
replaced. If type with sleeve bearing, this bearing should be they can be redressed with a fine piece of emery cloth or by
checked for scores and wear and replaced if necessary. lapping with a lapping stone, grinding compound and grinding
tool. If the seats are excessively damaged to the extent
UNLOADER MECHANISM
that they cannot be reclaimed, they should be replaced.
Used unloader mechanism should be replaced by unloader The dimension from the top of the cylinder block to the inlet
kits 265014 for Type Tu-Flo 400 compressors and 265015 valve seat should not exceed 0.118 in. nor be less than
for Types Tu-Flo 500 and 1000 compressors. The Tu-Flo 0.101 in.
1000 compressor requires two kits per compressor.
Slightly worn or scratched inlet valves can be reclaimed by
The new unloader pistons should be a loose sliding fit in the lapping them on a piece of fine crocus cloth on a flat surface,
unloader piston bores of the cylinder block. but it is suggested that new inlet valves be installed.
PARTS SPECIAL TO SELF-LUBRICATED ASSEMBLY
TYPE COMPRESSORS INSTALLING CYLINDER BLOCK
OIL PUMP SCREEN Position cylinder block gasket and block on crankcase
Check oil pump screen to be sure it is clean and not according to markings made prior to disassembly. Using
damaged; replace if damaged. cap screws with lock washers, secure cylinder block to
crankcase.
OIL PUMP PISTON AND BUSHING
INSTALLING CRANKSHAFT
Check fit of oil pump piston in base plate pump bushing. It
must be a medium sliding fit. If excessive clearance is If the crankshaft is fitted with oil seal rings, install rings.
found, the oil rod and/or bushing must be replaced. Position ball bearings and crankshaft in crankcase, making
sure the drive end of the crankshaft is positioned as marked
OIL PUMP RELIEF VALVE
before disassembly.
If the oil pump relief valve is defective, it should be replaced.
If one end of the crankcase is counterbored for holding a
OIL PUMP CHECK VALVE bearing, be sure the crankshaft is installed through the correct
The check valve should be replaced. It can be checked by end of the crankcase.
applying air pressure back through the pin stop end and Carefully press crankshaft and bearings into crankcase using
noting that the balI check seals on its seat. arbor press.
REPAIRS Position a new rear end cover gasket, when used, over the
rear end of the crankcase, making sure the oil hole in the
DISCHARGE VALVES AND SEATS gasket lines up with the oil hole in the crankcase. Position
If discharge valve seats merely show signs of slight wear, end cover with oil seal ring, if used, installed over crankcase
they can be dressed by using a lapping stone, grinding and end cover gasket. The end cover should be positioned
compound and grinding tool. Install new discharge valves correctly in relation to the oil holes in the gasket and
and valve springs. crankcase. Secure end cover to crankcase with cap screws
To test for leakage by the discharge valves, apply about 100 and lock washers.
pounds of air pressure through the cylinder head discharge If the opposite end cover requires an oil seal which was
port and apply soap suds at the discharge valves and seats. removed on disassembly, a new seal should be pressed
into end cover. Position new end cover gasket and carefully
10
main local global operation trouble-
menu search search shooting
install end cover over crankshaft and to crankcase, avoiding Install the unloader pistons in their bores with caution against
damage to the seal. Secure end cover with cap screw and cutting the grommets or distorting the back-up rings. Position
lock washers. unloader plungers in their guides and slip them in and over
the tops of the pistons.
PISTONS AND CONNECTING RODS
Install the unloader spring seat in the cylinder block; a small
If new wrist pin bushings are to be used, they should be
hole is drilled in the block for this purpose. Position the
pressed into the connecting rods so that the oil hole in the
saddle between unloader piston guides so its forks are
bushing lines up with the one in the rod. The new bushings
centered on the guides. Install the unloader spring, making
should then be reamed or honed to provide between 0.0002
sure it seats over the spring seats both in the block and on
in and 0.0007 in. clearance on the wrist pin. Position
the saddle.
connecting rod in piston and press in wrist pin so that
lockwire hole in the pin aligns with that of the piston. Install Install inlet valve seats if they have been previously removed.
new lockwire through piston and wrist pin and lock same by Position and install inlet valve guides, then drop inlet valves
snapping short end into lockwire hole at the bottom of the in their guides. There should be a loose sliding fit between
piston (Fig. 7). Teflon plugs in wrist pin ends may be used guides and valves.
instead of the lockwires (Fig. 21). CYLINDER HEAD ASSEMBLY
Install piston rings in correct location with ring pipmarks up If previously removed, the discharge valve seats should be
(Fig. 23). Stagger the position of the ring gaps. installed. Drop discharge valves into their seats. Install
Prelubricate piston, piston rings, wrist pin and connecting discharge valve springs and cap nuts.
rod bearings with clean engine oil before installing them in Place the inlet valve springs in the cylinder head. Use a
the compressor. small quantity of grease to hold them in place, just enough
Remove connecting bolts and bearing cap from one grease to keep the springs from falling out. Place cylinder
connecting rod. Turn crankshaft so one of its connecting head gasket on cylinder block. Carefully align cylinder head
rod journals is in the downward, center position. Compress assembly on block and install cap screws with lock washers.
the rings with a ring compression tool and insert the Tighten securely and evenly cap screws that hold cylinder
connecting rod with piston through the top of the cylinder head to block.
whose journal is down. Position and attach the bearing cap
to the connecting rod, making sure the bolt lock washers BASEPLATE
are properly positioned on the cap. Tighten connecting rod SELF-LUBRICATED TYPE COMPRESSORS
bolts evenly and bend the two new lock washer prongs up Install oil pump piston and rod on crankshaft.
against the hex head of the bolt. Install the other connecting Oil rod bearing fit must be the same as specified for
rod and piston in the same manner. connecting rod bearings. Install oil rod cap nuts and cotter
pins to lock oil rod nuts.
Install oil pump relief valve in base plate. The relief valve can
be tested at this stage by applying air pressure to the relief
valve. The valve should open when the pressure is between
14 psi minimum and 24 psi maximum. When the relief valve
is properly installed in the base plate, install set screw that
locks it in place.
Place oil pump screen in base and install retaining ring,
making sure it snaps in place and secures the screw.
Install oil filter fitting on base plate in its proper place. Install
blanking cover on opposite oil filter fitting hole in plate.
Install a new oil seal gasket around oil pump - check valve
and position a new base plate gasket on the crankcase.
FIGURE 24 - UNLOADER MECHANISM
Position base plate assembly on crankcase, making sure
oil pump piston engages the oil pump bushing in the base
UNLOADER MECHANISM (Fig. 24) plate. Install and tighten base plate screws.
The unloader pistons and their bores must be lubricated
with special lubricant piece number 239379 (dimethyl
polysiloxane) prior to installation. If new unloader kits are
being installed, the pistons in the kit are already lubricated.
11
main local global operation trouble-
menu search search shooting
BUILD-UP TIME
TYPE COMPRESSOR 0 TO 100 PSI
TU-FLO 400 47 SECONDS MAXIMUM
TU-FLO 500 30 SECONDS MAXIMUM
TU-FLO 1000 15 SECONDS MAXIMUM
During the above test the compressor should be checked
for oil leakage and noisy operation.
FIGURE 25 - AIR STRAINER - EXPLODED VIEW
IMPORTANT! PLEASE READ
When working on or around a vehicle, the following
AIR STRAINER general precautions should be observed:
If the compressor is type with air strainer, assemble strainer 1. Park the vehicle on a level surface, apply the parking
(Fig. 25). Using a new strainer gasket, install strainer on brakes, and always block the wheels.
cylinder block. 2. Stop the engine when working around the vehicle.
GOVERNOR 3. If the vehicle is equipped with air brakes, make certain
If compressor is type with pad mounted governor, install a to drain the air pressure from all reservoirs before
new or factory rebuilt governor using a new governor gasket. beginning ANY work on the vehicle.
4. Following the vehicle manufacturers recommended
INSPECTION OF REBUILT UNIT
procedures, deactivate the electrical system in a manner
Check to be sure that covers, plugs or masking tape are that removes all electrical power from the vehicle.
used to protect all ports if compressor is not to be installed
5. When working in the engine compartment the engine
immediately.
should be shut off. Where circumstances require that
Fit the end of all crankshafts with keys, nuts and cotter pins the engine be in operation, EXTREME CAUTION should
as required and then protect the ends against damage by be used to prevent personal injury resulting from contact
wrapping with masking or friction tape. with moving, rotating, leaking, heated, or electrically
The open bottom of engine lubricated compressors should charged components.
be protected against the entrance of dirt during handling or 6. Never connect or disconnect a hose or line containing
storage, by installing a temporary cover over base. pressure; it may whip. Never remove a component or
TESTING REBUILT COMPRESSOR plug unless you are certain all system pressure has
been depleted.
In order to properly test a compressor under operating
conditions, a test rack for correct mounting, cooling, 7. Never exceed recommended pressures and always wear
lubricating and driving the compressor is necessary. Such safety glasses.
tests are not compulsory if the unit has been carefully rebuilt 8. Do not attempt to install, remove, disassemble or
by an experienced person. assemble a component until you have read and
A compressor efficiency or build-up test can be run which is thoroughly understand the recommended procedures.
not too difficult. Before the test, the crankcase of a self- Use only the proper tools and observe all precautions
lubricated type compressor should be properly filled with pertaining to use of those tools.
lubricating oil. An engine lubricated compressor must be 9. Use only genuine Bendix replacement parts, components
connected to an oil supply line of at least 15 pounds pressure and kits. Replacement hardware, tubing, hose, fittings,
during the test and an oil return line must be installed to etc. should be of equivalent size, type, and strength as
keep the crankcase drained. The compressor (when tested) original equipment, and be designed specifically for such
should be tested without a strainer. applications and systems.
To the discharge port of the compressor, connect a reservoir 10. Components with stripped threads or damaged parts
or reservoirs whose volume plus the volume of the connecting should be replaced rather than repaired. Repairs requiring
line equals 1,300 cubic inches. Run the compressor between machining or welding should not be attempted unless
1,700 and 1,750 RPM. Elapsed time that the compressor specifically approved and stated by the vehicle or
takes to build up from 0 to 100 psi depends on the type component manufacturer.
compressor as follows: 11. Prior to returning the vehicle to service, make
certain all components and systems are restored
to their proper operating condition.
12
main local global operation trouble-
menu search search shooting
13
main local global operation trouble-
menu search search shooting
TABULATED DATA
Tu-Flo Tu-Flo Tu-Flo
400 500 1000
Number Cylinders 2 2 4
Bore Size 2.0625" 2.5" 2.5"
Stroke1. 5" 1.6875" 1.6875"
Displacement at 1,250 RPM 7.25 cu. ft./min. 12 cu. ft./min. 24 cu. ft./min.
Maximum recommended RPM 3,000 water cooled 3,000 water cooled 3,000 water cooled
2,400 air cooled 2,400 air cooled 2,400 air cooled
Minimum coolant flow at 2.5 gal./min. 2.5 gal./min. 2.5 gal./ min.
maximum RPM water cooled water cooled water cooled
250 CFM air flow 250 CFM air flow 250 CFM air flow
Approximate horsepower required
at 1,250 RPM 1.2 H.P. 2.3 H. P. 4.6 H. P.
Maximum inlet air temperature 250° F. 250° F. 250° F.
Maximum discharge air temperature 400° F. 400° F. 400° F.
Minimum pressure required
to unload 60 PSI 60 PSI 60 PSI
Minimum oil pressure required at
engine idling speed 5 PSI 5 PSI 5 PSI
Minimum oil pressure required at
maximum governed engine speed 15 PSI 15 PSI 15 PSI
Approximate average weight 34 lbs. 46 lbs. 75 lbs.
Oil capacity of self-lubricated model .53 qts. .53 qts. .95 qts. to 5 qts.*
Minimum discharge line size 1/2" O.D. tubing 5/8" O.D. tubing 5/8" O.D. tubing or equivalent
or equivalent or equivalent from each head to a common
manifold with 1" tubing from
manifold.
Minimum coolant line size 3/8" O.D. tubing 1/2" O.D. tubing 1/2" O.D. tubing
or equivalent or equivalent or equivalent
Minimum oil supply line size 1/4" O.D. tubing 1/4" O.D. tubing 1/4" O.D. tubing
or equivalent or equivalent or equivalent
Minimum oil return line size 1/2" O.D. tubing 5/8" O.D. tubing 5/8" O.D. tubing
or equivalent or equivalent or equivalent
**Minimum air inlet line size 5/8" I.D. 5/8" I.D. 1" I.D. if equipped with inlet
manifold; or, dual 5/8" I.D. lines
from engine to compressor inlets.
*Part Number dictates oil capacity
**Inlet line sizes specified for compressors with inlet connected to engine manifold.
1. Compressor passes excessive A. Restricted air intake. A. Check engine or compressor air cleaner and
oil as evidenced by presence replace if necessary. Check compressor air
of oil at exhaust ports of inlet line for kinks, excessive bends and be
valving or seeping from air certain inlet lines have the minimum
strainer. specified inside diameter. Recommended
minimum inlet line inside diameter is 5/8".
Recommended maximum air inlet restriction
is 25" of water.
B. Restricted oil return B. Oil return to the engine should not be in
(to engine). any way restricted. Check for excessive
bends, kinks, and restrictions in the oil
return line. Minimum recommended oil
return line size is 5/8" O.D. tubing or
equivalent I.D. (1/2" minimum). Return
line must CONSTANTLY DESCEND from
the compressor to the engine crankcase.
Make certain oil drain passages in the
compressor and mating engine surfaces
are unobstructed and aligned. Special
care must be taken when sealants are
used with, or instead of, gaskets.
14
main local global operation trouble-
menu search search shooting
C. Poorly filtered inlet air. C. Check for damaged, defective or dirty air
filter on engine or compressor. Check for
leaking, damaged or defective compressor
air intake components (i.e., induction line,
fittings, gaskets, filter bodies, etc). The
compressor intake should not be
connected to any part of the exhaust gas
recirculation (E.G.R.) system on the
engine.
D. Insufficient compressor D. For air-cooled compressor or air-cooled
cooling (compressor runs portions of the compressor:
hot). 1. Remove accumulated grease, grime, or
dirt from the cooling fins. Replace
components found damaged.
2. Check for damaged cooling fins.
Replace components found damaged.
3. Air-cooled compressors should not be
used on engines equipped with fan
clutches.
For water-cooled compressor or water-
cooled portions of the compressor:
1 . Check for proper coolant line sizes.
Minimum recommended size is 1/2"
O.D. tubing.
2. Check the coolant flow through the
compressor. Minimum allowable flow
is 2.5 gallons per minute at engine
governed speed. If low coolant flow is
detected, inspect the coolant lines and
fittings for accumulated rust scale, kinks
and restrictions.
3. Water temperature should not exceed
200 0 F.
4. Optimum cooling is achieved when
engine coolant flows into the com
` pressor cylinder block at one end and
out the compressor cylinder head at the
opposite end.
E. Contaminants not being E. Check reservoir drain valves to ensure
regularly drained from that they are functioning properly. It is
system reservoirs. recommended that the vehicle be
equipped with functioning automatic
drain valves, or have all reservoirs
drained to zero (0) psi daily, or
optimally to be equipped with a
desiccant-type air dryer prior to the
reservoir system.
F. Compressor runs loaded an F. Vehicle system leakage should not
excessive amount of time. exceed industry standards of onepsi
pressure drop per minute without
brakes applied, and three psi
pressure drop per minute with brakes
applied. If leakage is excessive,
check for system leaks and repair.
G. Excessive engine crankcase G. Test for excessive engine crankcase
pressure. pressure and replace or repair
crankcase ventilation components as
necessary. (An indication of
crankcase pressure is a loose or
partially lifted dipstick.)
H. Excessive engine oil H. Check the engine oil pressure with a
pressure. test gauge and compare the reading to
the engine specifications. Bendix
does not recommend restricting the
compressor oil supply line because of
the possibility of plugging the
restriction with oil contaminants.
Minimum oil supply line size is 1/4"
O.D. tubing.
I. Faulty compressor. I. Replace or repair the compressor only
after making certain none of the
preceding installation defects exist.
15
main local global operation trouble-
menu search search shooting
2. Noisy compressor operations. A. Loose drive gear or pulley. A. Inspect the fit of the drive gear on pulley on
the compressor crankshaft. The pulley on
gear must be completely seated and the
crankshaft nut must be tight. If the
compressor crankshaft surface or its
keyway are damaged, it is an indication of
loose drive components. If damage to the
compressor crankshaft is detected,
replace the compressor or the crankshaft.
When installing the drive gear or pulley,
torque the crankshaft nut to 100 foot
pounds. DO NOT BACK OFF THE
CRANKSHAFT NUT TO
ALIGN THE COTTER PIN AND
CASTELLATED NUT. (Some compressors
do not use castellated nuts.) DO NOT USE
IMPACT WRENCHES.
B. Excessively worn drive B. Inspect drive gear and couplings and engine
couplings or gears. for excessive wear. Replace as necessary.
(Non-metallic gears should be replaced
when the compressor is changed.) 501
drive gear should be metal-type on
Detroit Diesel engine.
C. Compressor cylinder head or C. Inspect the compressor discharge port and
discharge line restrictions. discharge line for carbon build-up. If
carbon is detected, check for proper
cooling to the compressor. (See Cause
and Remedy (D) under Symptom #1.)
Inspect the discharge line for kinks and
restrictions. Replace discharge line as
necessary.
D. Worn or burned out D. Check for proper oil pressure in the
bearings. compressor. Minimum required oil
pressure, 5 psi engine idling, 15 psi
maximum governed engine rpm. Check for
excessive oil temperature - should not
exceed 240° F.
E. Faulty compressor. E. Replace or repair the compressor after
determining none of the preceding installation
defects exist.
3. Excessive build-up and A. Dirty induction air filter. A. Inspect engine or compressor air filter and
recovery time. Compressor replace if necessary.
should be capable of building
air system from 85-100 psi in B. Restricted induction line. B.
Inspect the compressor air induction line
40 seconds with engine at for kinks and restrictions and
full governed rpm. Minimum replace as necessary.
compressor performance is C. Restricted discharge line or C. Inspect the compressor discharge port and
certified to meet Federal compressor discharge cavity. line for restrictions and carbon build-up.
requirements by the vehicle If a carbon build-up is found, check for
manufacturer. Do not proper compressor cooling.
downsize the original Replace faulty sections of the discharge
equipment compressor. line.
D. Slipping drive components. D. Check for faulty drive gears and couplings
and replace as necessary. Check the
condition of drive belts and replace or tighten,
whichever is appropriate.
E. Excessive air system leakage. E. Test for excessive system leakage and repair
as necessary. Use the following as a
guide: Build system pressure to governor
cutout and allow the pressure to stabilize
for one minute. Using the dash guage,
note the system pressure and the
pressure drop after two minutes.
The pressure drop for Pre-1975 vehicles
should not exceed:
1. 4 psi for a single vehicle.
2. 6 psi for a tractor trailer.
3. 10 psi for a tractor and 2 trailers.
The pressure drop for Post-1975 vehicles
should not exceed:
1. 2 psi in each reservoir for a single
vehicle.
2. 6 psi in each reservoir for a tractor and
16
main local global operation trouble-
menu search search shooting
trailer.
SYMPTOMS CAUSE REMEDY
4. Compressor fails to unload. A. Faulty governor or governor A. Test the governor for proper operation
installation. and inspect air lines to and from the
governor for kinks or restrictions. Replace
or repair the governor or its connecting air
lines.
B. Faulty or worn unloader B. Inspect for worn, dirty or corroded unloader
pistons or bores. pistons and their cylinder block bores.
Replace as necessary.
6. Compressor constantly cycles A. Leaking compressor A. Remove the compressor inlet air strainer
(compressor remains unloader pistons. or fitting. With the compressor unloaded
unloaded for a very short (not compressing air), check for air
time). leakage around the unloader pistons.
Replace as necessary.
B. Faulty governor. B. Test the governor for proper operation and
repair or replace as necessary.
C. Excessive system leakage. C. Test for excessive system leakage as
instructed in Symptom 3, Remedy E.
Reduce leakage wherever possible.
D. Excessive reservoir D. Drain reservoirs.
contaminants.
7. Compressor leaks coolant. A. Improperly installed plugs A. Check torque of fittings and plugs and
and coolant line fittings. tighten as necessary. Over-torqued fittings
and plugs can crack the head or block
casting.
B. Freeze cracks due to B. Test anti-freeze and strengthen as
improper anti-freeze necessary. Check coolant flow through
strength. compressor to assure the proper
anti-freeze mixture reaches the
compressor.
C. Faulty compressor (porous C. If casting porosity is detected, replace
castings). the compressor.
17
main local global operation trouble-
menu search search shooting
8. Compressor head gasket A. Restricted discharge line. A. Clear restriction or replace line.
failure.
B. Loose head bolts. B. Tighten evenly to a torque of 25-30 foot
pounds.
C. Faulty compressor or head C. Check for rough or poorly machined
gasket. head or block surfaces. Replace
necessary components.