Repairs; End Covers; Crankcase; Piston Rings - BENDIX TU-FLO 550 COMPRESSOR Manual

END COVERS

Check for cracks and external damage. If the crankshaft
main bearing (32) is installed in the end cover (34),
check for excessive wear and fl at spots and replace if
necessary.

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 .0003 in. tight to .0023
in. loose. This is to maintain the correct fi t. The compressor
must be replaced if the fi t is too loose.
On compressors fi tted with precision, sleeve main bearings,
the difference between the O.D. of the crankshaft journal
and the main bearing l.D. must not exceed .005 in. If the
clearance is greater than .005 in. the bearing must be
replaced.
The cylinder bores should be checked with inside
micrometers or calipers. Cylinder bores which are scored
or out of round by more than .0005 in. or tapered more than
.0005 in. should be re-bored 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.
SIDE CLEARANCE
.002
.004
STANDARD PISTON
RING
END GAP
FIGURE 12 - RING CONFIGURATION
EXPANDER
RING
OIL RING
End
Ring
Gap
.002
Compression
.013
.010
Segment
.040

PISTON RINGS

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 diametrical
clearance is between .002 in. minimum and .004 in.
maximum.
Check the fi t of the wrist pins to the pistons and connecting
rod bushings. The wrist pin should be a light press fi t in
the piston. If the wrist pin is a loose fi t, the piston and pin
assembly should be replaced. Check the fi t of the wrist
pin in the connecting rod bushing by rocking the piston.
This clearance should not exceed .0007 in. Replace the
connecting rod and cap assembly which includes the wrist
pin bushings if excessive clearance is found. Check the fi t
of the rings in the piston ring grooves. Check the ring gap
with the rings installed in the cylinder bores. Refer to Figure
12 for correct gap and groove clearances.
CRANKSHAFT
Check the crankshaft threads, keyways, tapered ends
and all machined and ground surfaces for wear, scores,
or damage. Standard crankshaft journals are 1.1242 in.
- 1.1250 in. in diameter. If the crankshaft journals are
excessively scored or worn or out of round and cannot be
reground, the compressor must be replaced. Connecting
rod bearing inserts are available in .010 in., .020 in.
and .030 in. undersizes for compressors with reground
crankshafts. Main bearing journals must be maintained
so the ball bearings are a snug fi t or so that no more than
.005 in. clearance exists between the precision sleeve main
bearing and the main bearing journals on the crankshaft.
Check to be sure the oil passages are open through the
crankshaft.
CONNECTING ROD BEARINGS
Used bearing inserts must be replaced. The connecting rod
.000
and cap are a matched set and therefore the caps must not
.006
be switched or rotated end for end. The solid inserts must
be installed in the rod and the slotted inserts into the cap.
Make sure the locating tangs on the inserts engage with
the locating notches in the rod and cap. Clearance between
the connecting rod journal and the connecting rod bearing
must not be less than .0003 in. or more than .0021 in. after
rebuilding.

REPAIRS

UNLOADER
A new cylinder head maintenance kit should be used when
rebuilding. Note: The entire contents of this kit must
be used. Failure to do so may result in compressor
failure. The unloader pistons in the kit are prelubricated