Table of Contents
Advertisement
GM COACH MAINTENANCE MANUAL
Sec. 4
Page 67
3. Discharge Valves
If
discharge valves are not worn excessively
or damaged, they may be cleaned by lapping them
on a piece of crocus cloth on a flat surface.
4. Oil Passages
Thoroughly clean all passages through crank-
shaft, connecting rods, crankcase, and rear end
cover.
If
necessary, prod oil passages with a
piece of wire, flush with cleaning fluid, and blow
out with compressed air.
5. Cylinder Block
Soak cylinder block in cleaning fluid to loosen
carbon and dirt from intake manifold and intake
ports. Blow dirt out with compressed air.
6.
Pistons
Scrape all carbon and dirt out of ring grooves
in pistons.
Make sure drain holes in oil ring
grooves are open.
7. Ball Bearings
Immerse bearings in cleaning fluid, clean with
a brush to remove old lubricant. Blow bearings
dry with compressed air, then wrap in a clean
cloth.
INSPECTION
L
Cylinder Head
Inspect cylinder head body for cracks or breaks;
replace head if any are found. Check condition of
unloading diaphragm seat in diaphragm cavity.
Replace cylinder head body if seat is damaged in
any way.
Inspect unloading valve seats in bottom
of cylinder head.
If
seats are pitted or worn they
must be reamed as directed later in this section
under "Compressor Repair."
Test cylinder head
water jacket for leakage, using air pressure. Re-
place cylinder head body if leakage is evident.
2. Unloading Lever Pin
Check fit of unloading lever pin in unloading
lever.
If
excessive play is evident, replace lever
or pin, or both.
3. Unloading Diaphragms and Cover
Inspect diaphragms and replace if any signs
of wear or cracking are present.
Examine dia-
phragm seat on bottom of diaphragm cover.
Lap
seat or replace cover as necessary.
4. Unloading Valves and Bushings.
Check fit of unloading valve stems
in
unload-
ing valve bushings; valve stems must be a neat
sliding fit in bushings.
If
excessive clearance is
evident, check valve stems for wear.
Wear of
the valve stems must not exceed .002 inch. Wear
may be checked by comparing the diameter of the
valve stem where it engages the bushing with the
diameter of the stem where it does not engage
the bushing.
If
clearance between valve stems
and bushings is excessive, valves, bushings, or
both must be replaced as directed later under
"Compressor Repair" in this section.
AIR COMPRESSOR AND GOVERNOR
5. Discharge Valve Springs
Discard all used discharge valve springs and
replace with new springs.
6. Discharge Valves and Seats
Inspect discharge valves and seats.
If
dis-
charge valves are grooved deeper than .003 inch
where they contact the seats, they must be re-
placed. Valves which are scratched or only slightly
grooved may be repaired by lapping valves with
a fine abrasive powder on a surface plate.
If
discharge valve seats are worn or pitted, they
must be reconditioned as directed later under
"Compressor Repair" in this section.
7. Crankcase and End Cover
Check crankcase and end cover for cracks or
broken lugs. Replace with new parts
if
damaged.
Check fit of oil seal ring in groove in rear end
cover.
Ring must be a neat fit in groove and
must have .008 to .015 inch clearance at the gap
when placed in the end bore of the crankshaft.
8. Crankcase Bearing Bores
Check fit of ball bearings in crankcase. Bear-
ings must be a light press fit in bores.
If
crank-
case bearing bores are worn or damaged, crank-
case must be replaced.
9. Cylinder Block
If
cylinder block is cracked or damaged in any
way, it must be replaced. Examine cylinder bores
for scoring, out-of-round, and taper. Bores may
be checked for out-of-round and taper using an
inside micrometer as shown in figure 21.
Bores
which are scored or out-of-round more than .003
inch, or tapered more than .003 inch must be re-
bored, ground, or honed oversize.
Pistons are
available in .010, .020, and .030 inch oversize.
Cylinder bores must be smooth, straight, and
round, and must be finished with a 500 (or finer)
grit hone.
Clearance between piston and cylinder
wall must not be less than .002 inch or more
than .004 inch.
10. Pistons
Examine pistons for scoring, cracks, or dam-
age of any kind.
Measure outside diameter of
piston with a micrometer and compare this meas-
urement with inside diameter of cylinder bore.
If
piston is more than .004 inch smaller than the
cylinder bore, piston must be replaced with an
oversize piston.
11. Piston Pins
Check fit of piston pins in pistons and con-
necting rods.
Pins must be a light press fit in
pistons.
If
piston pin is loose in piston, the pin,
piston, or both must be replaced.
Check fit of
piston pins in connecting rod bushings by rocking
the pins in the bushings.
If
looseness is evident,
replace the connecting rod bushings as directed
later under "Compressor Repair" in this section.
Discard all used piston pin locks.
Advertisement
Table of Contents
