condition requires that the cooling system be drained
Coolants and Antifreeze
and flushed.
Since water is easily obtained, cheap, and has the
NOTE: Old coolant must be contained and treated
ability to transfer heat readily, it has served as a basic
as hazardous material. For detailed instructions, see
coolant for many years. Some properties of water, such
your equipment manuals and shop instructions.
as its boiling point, freezing point, and natural
A cleaning compound can be used to remove rust
corrosive action on metals, limit its usefulness as a
and scale from the system. In using the compound, you
coolant. To counteract this, antifreeze is used. The
m u s t b e c a r e f u l t o f o l l ow t h e m a n u fa c t u r e r 's
most commonly used type of antifreeze is ethylene
instructions. Following this, the system should be
glycol. It is chemically compounded of a mixture of
neutralized, since cleaners contain strong acids that, if
ethylene and glycerin derivatives and is manufactured
not completely removed, attack parts of the cooling
under many trade names. A normal mixture of
system.
antifreeze is usually 50-percent ethylene glycol and
5 0 - p e r c e n t w a t e r ; h ow ev e r, c h e c k w i t h t h e
maintenance instruction manual (MIM) for each
WARNING
specific type of equipment for the proper mixture.
Engine cooling system cleaning compound is
Maximum freezing protection is achieved by mixing
poisonous and may be fatal if swallowed. Avoid
60-percent ethylene glycol with 40-percent water.
contact with your eyes or prolonged contact with
This will protect the cooling system to about -62F.
your skin. Avoid spilling compound on the painted
Ethylene glycol has a very high boiling point, does not
surface of the vehicle.
evaporate easily, and is noncorrosive and practically
nonflammable.
S o m e m a n u fa c t u r e r s r e c o m m e n d r eve r s e -
SERVICING THE LIQUID-COOLING
flushing; for example, forcing water and air through
SYSTEM
the system in the direction opposite to normal
circulation. This tends to loosen the scale and flush it,
Because the effects or damages that result from an
along with any sediment, out of the system.
improperly serviced cooling system usually occur
Some AS shops are equipped with
gradually, this system tends to be neglected. However,
reverse-flushing equipment. It usually consists of a
the requirements of modern liquid-cooled engines and
flushing gun device similar to that shown in figure 5-9.
the severe conditions under which they often operate
In the figure, a gun is being used on the radiator that has
make it necessary that the cooling system be
been filled with water and the cap installed. Notice that
m a i n t a i n e d a t m a x i m u m e ff i c i e n c y. T h i s i s
the lower radiator hose has been disconnected from the
particularly true in the case of V-8 engines, especially
water pump and that the gun is used to force water and
the larger ones, because of the increase in the heat
air through this hose and into the radiator. The air
generated and the slight margin of safety provided by
pressure is applied intermittently to loosen scale and
the design of the cooling system. In fact, only a slight
sediment better. Excessive air pressure should be
loss in circulation or cooling efficiency can be critical.
avoided to prevent damage to the radiator. Starting and
When the vehicle is loaded with power equipment, it
stopping the flow of water produces a fluctuation of
places an additional load on the engine at idle or in
pressure and tends to loosen all foreign matter clinging
slow traffic on hot days. In view of this, it is essential
to the water passages in the radiator core. As shown in
that proper inspection and servicing be accomplished
figure 5-9, the upper hose has been disconnected from
to keep the cooling system in good condition. Proper
the engine so that the water can be directed to suitable
servicing includes cleaning and flushing, rust
disposal containers.
prevention, use of antifreeze, and cooling system
Reverse-flushing equipment can also be used, as
testing.
shown in figure 5-10, to reverse-flush the engine block
and head. First, remove the thermostat and disconnect
Cleaning and Flushing
the upper radiator hose between the water outlet and
Accumulations of rust and scale in the cooling
the radiator. Then disconnect the lower radiator hose at
system eventually restrict the circulation of coolant,
the water pump and insert the flushing equipment in
and the engine is likely to overheat. Correcting this
the upper radiator hose. Reverse-flush the system by
5-9
