54
18. After 1-2 hours of normal operating temperatures,
stop the compressor, lock it out from electrical sources,
and retighten the valve hold down screws and cylinder
head bolts to proper tightness.
VALVE REPLACEMENT
NOTICE: Suction and discharge valves must be
installed in the correct cylinder head locations. To
avoid confusion, work only on the inlet or the discharge
valves at one time, or tag the valves and valve pockets
with a note to indicate suction or discharge.
NOTICE: It is critical that the valve hold-down screws
be backed out when changing a valve, as the valve
cover plate may crack if the new valve is slightly taller
than the previous valve and the valve cover plate is
torqued to fi nal tightness.
ALL MODELS EXCEPT: 2WN150L, 2WN150H
1. Remove unloader piping from unloader
towers and unloader controls.
2. Unloaded suction valves:
a. Remove the unloader assembly. Remove and
discard unloader gaskets. Remove hold-down
screw with appropriate spanner wrench.
b. Remove valve cover. Discard valve cover
gasket.
c. Remove the valve clamp and unloader tube, the
unloader platform, and additional valve clamp on
certain models. Remove valve assembly and
discard valve seat gasket.
d. Disassemble the valve and inspect the valve seat,
plate, spring, guide and unloader fi ngers/springs
for wear. Repair or replace as necessary. Valve
seats can be lapped to remove minor damage.
Valve plates should be replaced if damaged.
Turning over a damaged valve plate will lead
to premature failure of the plate and possible
damage downstream from debris. Valve and
unloader springs and valve guides should be
replaced if in doubt.
e. Reassemble the valve in the reverse order it was
disassembled. Check for free movement of the
valve plate.
f. Reinstall a new valve seat gasket into the valve
pocket. Install valve assembly, verifying correct
valve orientation. The inlet valve plate should
move down when pushed from above with a
probe.
g. Install lower clamp (on certain valve models),
unloader fi ngers, springs & platform. Install
valve clamp.
3. Discharge valves and non-unloaded suction
valves:
a. Remove the valve hold-down screw nut (P/N
FQ003 or FQ004). Remove the valve hold-down
screw with an Allen wrench
b. Remove the valve cover and discard valve cover
gasket.
c. Remove the clamp and/or spacer, valve
assembly and valve gasket.
d. Disassemble the valve and inspect the valve
seat, plate, spring and/or, guide. Repair or
replace as necessary. Valve seats can be lapped
to remove minor damage. Valve plates should be
replaced if damaged. Turning over a damaged
valve plate will lead to premature failure of the
plate and possible damage downstream from
debris. Valve springs and guides should be
replaced if in doubt.
e. Reassemble the valve in the reverse order it
was disassembled. Check for free movement of
the valve plate. Tighten valve stud to specifi ed
torque.
f. Reinstall a new valve seat gasket into the valve
pocket. Install valve assembly, verifying correct
valve orientation. Inlet valves placed upside
down act as discharge valves, and vice-versa.
The inlet valve plate should move down when
pushed from above with a probe. The discharge
valve plate should NOT move when pushed from
above with a probe.
g. Install valve clamp and/or spacer.
4. Lightly lap top of valve cover at seating surface for
unloader tower assembly or valve hold-down screw
nut. Lap mating faces of unloader towers and valve
hold-down nut. While the unloader towers use a gasket
to seal and do not need fi ne lapping, the hold-down
screw nut, P/N FQ003, is a metal to metal contact and
should be well lapped to insure positive seal. The hold-
down screw nut PN FQ004 utilizes an O-ring - replace
it.
5. Install valve cover with new valve cover gasket.
Use compatible gasket sealant if acceptable. Torque
cap screws to proper tightness.
6. Install and torque the hold-down screw to proper
tightness.
7. Install the valve hold-down screw nut or unloader
tower and gasket. Torque to fi nal tightness.
8. Rotate the fl ywheel by hand to insure there is no
interference between the valves and pistons. Also
listen for air moving across the valves.
9. Reinstall unloader tubing.
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