leaving the engine than to circulate the water more slowly and have a larger difference in entering and
leaving temperatures.
Water in the cooling system is treated to remove hardness, to minimize corrosion, and to remove
suspended impurities. Hardness, a term used to express the presence of scale-forming salts in raw water,
can be removed by a water softener. Dry compounds should not be poured into the radiator as they may
clog the system. Water should be treated in a separate container first and solids allowed to settle before
drawing solution off for the engine. If treatment is improper or ineffective, radiators and water jackets
will become clogged and cylinder liners corroded.
1.8.
LUBRICATING SYSTEM
Sometimes, oil is used for cooling as well as for lubricating. When this is done, a separate oil
radiator with its own cooling fan is provided with the main radiator. Used for bearing lubrication, the
oil's circulation rate is lower than when it is used for piston cooling and lubrication. Oil hits the
underside of the piston in a fine spray. The crankshaft, end bearings, operating gear, and camshaft are
lubricated by oil under pressure; oil without pressure, free return oil, lubricates the camshaft driving
gears and cylinder walls. Contaminating particles can usually be filtered out.
a. Contamination. Some contamination of oil is inevitable. For example, the oil itself will
oxidize and form corrosive acids. These acids are prevented from harming the engine by additives
which either keep the oil from oxidizing or provide a protective coating on the parts they touch. In
addition, the oil should possess some detergent properties to keep the contaminating matter in
suspension so that it will be drained off when the crankcase is drained. Contaminating materials found
in the oil may be any of the following: metal bits caused by wear of the engine, carbonaceous particles
resulting from fuel incorrectly burned or caused by breakdown of the oil itself, unburnt fuel, cooling
water that has leaked in, and acid water caused by cooling of burnt gases which have passed by the
piston.
b. Filters. Oil circulation pumps are protected from contamination by gauze screens that
remove the heavier substances from the oil; smaller particles are removed by metallic strainers made of
very fine gauze, steel wool, or closely spaced plates. The finest materials and carbon carried in
suspension in the oil are removed by absorbent filters made of special papers, cotton, or felt. Two
methods of routing the oil through the filters are used: full -
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