Fluids include brake fluid, hydraulic fluid, and
other moving parts of the engine subject to friction)
automatic transmission fluid.
must be bathed in oil at all times.
BRAKE FLUID.--Most hydraulic brake systems
GREASES.--Greases are compounds of oil and
use a nonpetroleum-based hydraulic brake fluid, such
soap. The soaps used are not ordinary laundry soaps but
as specification VV-H-910 or VV-B-680.
animal fats mixed with certain chemicals. The main
purpose of the soap is to provide a body or carrier for
the oil that actually does the lubricating.
Grease is used where oil is impractical or
unsatisfactory due to centrifugal force, load, tem-
DO NOT mix petroleum-based or
perature, or exposure. For instance, in wheel bearings,
mineral-based hydraulic fluid (such as
grease maintains a lubricating film under heavy loads
MIL-H-5606B) with synthetic-based brake fluid.
and when the equipment is stationary for long periods
Attempts to combine the two results in formation
of a jelly substance, followed by decomposition
of the natural rubber seals and system failure.
Grease is separated into broad classifications, such
Consult the lubrication chart for the particular
as chassis, cup of water pump, wheel bearings,
unit before servicing any hydraulic system, and
and general-purpose grease, and so on. Many
use only the fluid recommended by the
special-purpose greases are manufactured. Among
these are distributor cam lobe lubricant, electric motor
bearing grease, and preservation grease.
HYDRAULIC FLUID.--Hydraulic fluid is used
in support equipment, such as hydraulic test stands,
forklifts, aircraft jacks, and spotting dollies. Most
Severe damage can result from too much or
hydraulic fluids are red in color and come in containers
too little lubrication, as well as from the use of the
ranging from 1 quart to 55 gallons. Many types of
wrong type of lubricant.
hydraulic fluids are available. They can be
synthetic-based or petroleum-based fluids. NEVER
MIX THE TWO. Always refer to the manufacturer's
You must ensure that the proper grease is used for
recommendations before servicing any unit.
the job. For example, chassis grease used on a
AUTOMATIC TRANSMISSION FLUID.--The
distributor cam lobe causes arcing and burning of the
majority of support equipment that have automatic
breaker points as the grease melts and is thrown onto
transmissions are designed to use type A automatic
the breaker points by centrifugal force. You can find
transmission fluid. Also, this fluid is used in the
information as to the proper grease to use in the
majority of power steering systems. The correct fluid
lubrication charts for the unit being serviced.
for your equipment is listed in the technical manual.
Fluid is the means by which energy is transmitted
Most multi-cylinder engines used in automotive
from the pump to the various units to be started. To
and support equipment use a liquid cooling system.
operate efficiently in a system, a fluid must have certain
Any liquid used in this type of system is called a
properties and characteristics.
"coolant." Water and antifreeze solutions are used as
It must flow freely at extremely high and low
NOTE: Water used in radiators should be clean and
It must be noncorrosive to metals and must not
should be checked often for cleanliness and quantity.
react chemically on the seals and packing used
A vehicle operated in temperatures below 32F
in the system.
requires an antifreeze solution in its cooling system.
It must have good lubricating qualities and be
Without this solution, the water in the cooling system
can freeze and cause extensive damage.