SkyTrak 6036 Service Manual - Manual (Page 281)

8.65 Model 6036 Legacy
Hydraulic System
f. Pump Inspection
1. Inspect internal pump components for wear, damage,
etc. If inner surfaces of the pump DO NOT display an
ultra-smooth, polished finish, or are damaged in any
way, replace the damaged part. Often, dirty hydraulic
fluid causes failure of internal pump seals and
damage to the polished surfaces within the pump
and other hydraulic system components.
2. If a dowel (Fig. 8-31, 7) or dowel-mounting hole is
damaged, replace the dowel or housing as required.
3. Examine thrust plates (Fig. 8-31, 11) for wear,
scoring, erosion, pitting, discoloration, abrasions or
other damage and replace if necessary. The thrust
plates seal the gear set at the sides. Worn thrust
plates allow internal slippage (oil bypasses the
pump). A maximum 0.002" (0,05 mm) of wear is
allowable.
Check the center of the thrust plates, where the
gears mesh together. Erosion at the center of the
thrust plates indicates oil contamination. Pitted
thrust plates indicate cavitation or oil aeration.
Discolored thrust plates indicate overheating, most
likely due to low hydraulic oil level in the reservoir.
4. Examine the gear set (Fig. 8-31, 12). Replace the
gears as a matched set if there is any scoring
(particularly scoring on the gear hubs), grooves or
burrs on the outside edges of the teeth, or any nicks,
grooves, frets or other damage to teeth surfaces.
5. Examine the housings (Fig. 8-31, 2, 3 and 4) and
replace if necessary. Place a straightedge across
each bore. Attempt to slip a 0.007" (0,18 mm) feeler
gauge under the straightedge and into the bore. If
bore wear is moderate, 0.007" (0,18 mm) or less, the
housing may be reused. If wear or distortion
exceeds 0.007" (0,18 mm), replace the housing and
examine the gear set (12) for wear. Replace as
required.
Operating pressure pushes the gears against the
low-pressure side of the housing. As the hubs wear,
the bore increases. Excessive bore expansion in a
short period of time indicates excessive pressure or
oil contamination. If the relief valve settings are
within prescribed limits, check for shock pressures or
tampering. Check an oil sample and the reservoir for
dirt.
Note: ALWAYS replace seals, o-rings, gaskets, etc., with
new parts to help ensure proper sealing and operation.
Lubricate seals and o-rings with clean hydraulic oil.
6. A seal kit (Fig. 8-31, 14) is available. Replace all
flexible seals, including the square “R” seal (8), lip
seal (13), back-up seals (10) and channel seals (9).
g. Pump Assembly
1. Stone all surfaces with a medium grit carborundum
stone or equivalent.
Note: Carborundum is boron nitride (c-BN) with cubic or
“diamond” molecular structure. c-BN is a hard, abrasive
composition.
2. Rinse all parts in an approved solvent. Blow dry and
wipe the parts with a clean, lintless cloth before
beginning assembly.
3. Coat the outer edge of the new lip seal (Fig. 8-31, 13)
with a non-hardening sealant (Permatex
®
Aviation
Form-A-Gasket No. 3 or equivalent). With the metal
side of the lip seal facing up, press the seal into the
mounting flange side of the shaft end cover with an
arbor press and a suitable lip seal driver. DO NOT
damage the lip seal. Press the seal into the housing
until the lip is flush with the housing recess. Wipe off
excess sealant.
4. Place the SEC housing (Fig. 8-31, 2), with the
transmission-mounting surface down, in a suitable
holding device or bench vise if possible.
5. Install new dowels (Fig. 8-31, 7) as required. Verify
that dowels are clean and free of burrs. Gently tap
the dowels into place with a soft hammer.
6. Lubricate both new square “R” seals (Fig. 8-31, 8)
with clean hydraulic oil. Insert the seals into their
grooves in each side of the gear housing (4).
7. Place new channel seals (Fig. 8 -31, 9) into the
grooves in both thrust plates (11) with the flat side of
the seal facing away from the thrust plate.
8. Place a new back-up seal (Fig. 8-31, 10) into the
grooves in both thrust plates (11) above the channel
seals (8).
9. Install one thrust plate (Fig. 8-31, 11) with channel
(9) and back-up (10) seals into the SEC housing (2),
so that the groove in the thrust plate will face away
from the gear housing (4). The flat side of the seal
should face down with the relief groove facing the
outlet side of the housing.
10. Lubricate the gear set (Fig. 8 -31, 12) with clean
hydraulic oil from a filtered source. Carefully slide the
gear set into position within the SEC housing (2).
Avoid damaging the lip seal (13) when the driven
gear passes through the housing. Apply additional
oil to the gears after installation.