Bendix Commercial Vehicle Systems TU-FLO 501 AIR COMPRESSOR 9/04 - Manual (Page 8)

8
OIL PASSING
All reciprocating compressors currently manufactured will
pass a minimal amount of oil. Air dryers will remove the
majority of oil prior to entrance into the air brake system.
For particularly oil sensitive systems the Bendix
® PuraGuard ®
QC ™ oil coalescing filter can be used in conjunction with a
Bendix air dryer.
If compressor oil passing is suspected, refer to the
TROUBLESHOOTING section and TABLE A for the
symptoms and corrective action to be taken. In addition,
Bendix has developed the "Bendix Air System Inspection
Cup" or BASIC test to help substantiate suspected excessive
oil passing. The steps to be followed when using the BASIC
test are presented in APPENDIX A at the end of the
TROUBLESHOOTING section.
INSPECTION OF PARTS
Cylinder Head Body
Inspect the cylinder head for cracks or damage. Apply shop
air pressure to one of the coolant ports with all others
plugged, and check for leakage by applying a soap solution
to the exterior of the body. If leakage is detected, replace
the head.
End Covers
Check for cracks and external damage. If the crankshaft
main bearings are installed in the end cover, check for
excessive wear and flat spots and replace them if necessary.
If the compressor has an oil seal in the end cover, it should
be removed by pressing it out of the end cover.
Crankcase
Check all crankcase surfaces for cracks and damage. On
compressors where ball bearing main bearings are used the
difference between the O.D. of the outer race and the I.D. of
the crankcase hole should be .0000 in. to .0015 in. loose.
This is to maintain the correct press fit. The crankcase must
be replaced if the fit is too loose.
On compressors fitted with precision, sleeve main bearings,
the difference between the O.D. of the crankshaft journal
and the main bearing I.D. must not exceed .0065 in. If the
clearance is greater than .0065 in., the end cover or main
bearing must be replaced.
Check the unloader bore bushings to be sure they are not
worn, rusted, or damaged. If these bushings are to be
replaced, they can be removed by running a 1/8 in. pipe
thread tap into the bushing, and inserting a 1/8 in. pipe
threaded rod and pulling the bushing straight up and out.
Do not use an easy-out for removing these bushings. If the
inlet valve seats are worn or damaged, so they cannot be
reclaimed by facing, they should be replaced. Cylinder
bores should be checked with inside micrometers or
calipers. (Fig. 11). Cylinder bores which are scored or out of
round by more than .001 in. or tapered more than .002 in.
should be rebored or honed oversize. Oversized pistons and
piston rings are available in .010 in., .020 in. and .030 in.
oversizes. Cylinder bores must be smooth, straight, and
round. Clearance between the cast iron pistons and cylinder
bores should be between .002 in. minimum and .004 in.
maximum.
FIGURE 11 - MEASURING CYLINDER BORES
FIGURE 12 - CORRECT GROOVE CLEARANCE
PISTON RING OIL RING
.001”
.003”
.002”
.004”
CORRECT GAP CLEARANCE
WITH RINGS IN CYLINDER
.002”
.010”
EXPANDER RING
OIL RING
PISTON RING
Pistons
Check the pistons for scores, cracks, or enlarged ring
grooves; replace the pistons if any of these conditions are
found. Measure each piston with a micrometer in relation
to the cylinder bore diameter to be sure the diametral
clearance is between .002 in. minimum and .004 in.
maximum.
Check the fit of the wrist pins to the pistons and connecting
rod bushings. The wrist pin should be a light press fit in the
piston. If the wrist pin is a loose fit, the piston and pin
assembly should be replaced. Check the fit of the wrist pin
in the connecting rod bushing by rocking the piston. This
clearance should not exceed .0007 in. Replace the wrist pin
bushings if excessive clearance is found. Wrist pin bushings
should be reamed to between .5314 in. and .5317 in. after
being pressed into the connecting rods.
Check the fit of the piston rings in the piston ring grooves.
Check the ring gap with the rings installed in the cylinder
bores. Refer to Fig. 12 for correct gap and groove clearances.