JLG 150HAX ANSI Service Manual - Manual (Page 126)

SECTION 5 - HYDRAULICS
5-30 – JLG Lift – 3120679
DRIVE SHAFTS
Replace if there is any wear detectable by touch in the
seal area or at the drive coupling. 0.002 inches (0.05 mm)
wear is the maximum allowable.
Wear in the shaft seal area indicates oil contamination.
Wear or damage to splines, keys, or keyways necessitates
replacement.
THRUST PLATES
The thrust plates seal the gear section at the sides of the
gears. Wear here will allow internal slippage, meaning oil
will bypass the pump.
A maximum of 0.002 inches (0.05 mm) wear is allowable.
Replace thrust plates if they are scored, eroded, or pitted.
Check center of thrust plates where the gears mesh. Ero-
sion here indicates oil contamination.
Pitted thrust plates indicate cavitation or oil aeration.
Discolored thrust plates indicate overheating, probably
insufficient oil.
DOWEL PINS
If either the dowel or dowel pin hole is damaged, the
dowel or machined casting, or both must be replaced.
If more than reasonable force is required to seat dowels,
the cause may be poorly deburred or dirty parts; cocking
of dowel in the hole; or improper pin-to-hole fit.
BUSHINGS
If gears are replaced, bushings must be replaced. Bush-
ings should fit into bore with a heavy press fit.
SEALS AND GASKETS
Replace all rubber and polymer seals, including all o-
rings, thrust plate channel seals, shaft seal, and gasket
seal.
PLUGS
Examine the plugs in the shaft end and port end cover to
make sure they are in the proper position and tight.
Recommended Start-up Procedure for New
or Rebuilt Pump
Before installing a new or rebuilt pump, back off the main
relief valve until the spring tension on the adjusting screw
is relieved. This will avoid the possibility of immediate
damage to the replacement unit in the event that the relief
valve setting had been increased beyond the recom-
mended operating pressure prior to removing the old unit.
Before connecting any lines to the pump, fill all ports with
clean oil to provide initial lubrication. This is particularly
important if the unit is located above the oil reservoir.
After connecting the lines and mounting the replacement
unit, operate the pump at least two minutes at no load and
at low rpm (400 min.) During this break-in period, the unit
should run free and not develop an excessive amount of
heat. If the unit operates properly, speed and pressure
can then be increased to normal operating settings.
Reset the main relief valve to its proper setting while the
pump is running at maximum operating engine (motor)
speed for the vehicle.
Recommended Test Procedure
Be sure there is an adequate supply of oil for the pump, at
least one gallon of oil for each gpm of pump capacity.
If one section of a tandem pump is being tested, make
sure that all other sections not being tested are ade-
quately supplied with oil. If any of the other sections run
dry, or if plugs are left in ports, serious and permanent
damage will result.
The oil should be a good quality hydraulic oil rated at
150SSU at 100°F., with the oil temperature held at 120° F.
plus or minus 5° F. (Test procedures are described in
detail in SAE handbooks; see Hydraulic Power Pump Test
Procedure, SAE J745c.)
The feed line must be of adequate size with no more than
5" mercury vacuum adjacent to the pump inlet. As a rule,
the feed line must provide a feed flow velocity not in
excess of 8 feet per second.
Feeding hot oil into a cold pump may cause the pump to
seize. Jog the pump by momentarily starting the driving
engine or motor to gradually equalize pump and oil tem-
peratures.