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PROBABLE CAUSES
NOISY PUMP
Air in the system: Check ttings, cracked
hoses and other parts on the pump intake.
Check hydraulic tank. The tank must be kept
3/4 full.
CAUTION: Never ll hydraulic tank com-
pletely full at any time. System drainage will
cause the tank to overll and spill out.
Cavitation (vacuum in pump): Check for
clogged or restricted intake line or plugged
air vent in tank.
Loose or worn pump parts: Look for worn
gaskets and replace if necessary. Check for
clean and proper uid.
Stuck pump vanes, valves, pistons etc:
Disassemble and clean thoroughly. Avoid
the use of les, emery cloth, steel hammers
etc, on a machined surface. Products of
uid deterioration such as gums, sludges,
varnishes and lacquers may cause sticking.
Use solvent to clean parts and dry thorough-
ly before reassembling. If parts are stuck by
corrosion or rust, they will probably have to
be replaced.
Pump out of alignment with drive: Check
alignment. Misalignment may be caused by
temperature variation.
OVERHEATING
Viscosity too high: Check recommenda-
tions. Unusual temperature conditions may
cause uid of proper viscosity for working
temperature to thicken too much on the way
to the pump. In this case, use of a uid with
higher viscosity index may cure trouble.
High discharge pressure: Such parts
may cause undue friction. Look for signs of
excessive friction. Be sure all parts are in
alignment.
Low oil: Maintain proper oil level, at least
3/4 full. If the tank is low, less uid will be
available to carry away the heat, raising the
oil temperature.
PUMP NOT PUMPING
Pump shaft turning in the wrong direc-
tion: Shut down immediately. Some types of
pumps
can turn in one direction only.
Intake clogged: Make sure tank is cleaned
periodically. Fluid must be kept 3/4 full.
Air leak in intake: If any air is going
through pump, it will cause noise. Pour uid
over points suspected of leakage; if noise
stops, you have found the leak.
Oil too heavy: If uid is too heavy, some
types of pumps cannot pick up prime. Fluid
that is too heavy can do great damage to
hydraulic systems. Drain and rell with oil of
the proper viscosity.
LOW PRESSURE IN SYSTEM
Relief valve setting too low: With an im-
proper setting, uid may ow from the pump
through the relief valve and back to the tank
without reaching the point of use. To check
relief setting, block pressure line beyond
relief valve and check line pressure with a
pressure gauge
Relief valve stuck open: Clean dirty relief
valves (see maintenance.) A stuck valve
may be an indication that the system con-
tains dirty or deteriorated hydraulic oil.
Broken, worn or stuck pump parts: In-
stall pressure gauge and block system just
beyond relief valve. If no noticeable pres-
sure is developed and relief is okay, look for
mechanical trouble in pump. Replace worn
and broken parts.
Valves sticking or binding: Check sus-
pected parts for mechanical problems such
as misalignment, bent, worn etc then look
for signs of dirt, sludge, varnishes and lac-
quers caused by deterioration.
Sluggishness when machine is rst start-
ed: Sluggishness is often caused by uid
that is too thick at starting temperatures. If
you can put up with this for a few minutes,
uid may thin out enough to give satisfac-
tory operation, but if it does not thin out or if
surrounding temperature remains relatively
low, you may have to switch to a uid with a
lower pour point and lighter viscosity. Under
severe conditions, immersion heaters are
sometimes used.
SERVICING HYDRAULICS
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