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engine and water may accumulate in the crankcase from con-
densation of moisture produced by the burning of the fuel.
Water, in the crankcase, may freeze and interfere with proper
oil circulation. It also promotes rusting and may cause clogging
of oil screens and passages. Under normal driving conditions
this water is removed by the crankcase ventilator. But if water
accumulates it should be removed by draining the crankcase
as frequently as may be required.
It is always advisable to let the engine reach normal operat-
ing temperature before draining the crankcase. The benefit of
draining is, to a large extent, lost if the crankcase is drained
when the engine is cold as some of the suspended foreign ma-
terial will cling to the sides of the oil pan and will not drain
out readily with the slower moving oil. Flushing the crankcase
with oils or solutions other than a good grade of SAE lOW
engine oil is not recommended.
Crankcase Dilution
Probably the most serious phase of engine oil deteriora-
tion is that of crankcase dilution, which is the thinning of
the oil by fuel vapors leaking by the pistons and rings and
mixing with the oil.
Leakage of fuel, or fuel vapors, into the oil pan mostly
occurs during the "warming-up" pe~iod, when the fuel is not
thoroughly vaporized and burned.
Automatic Control Devices to Minimize Crankcase Dilution.
The Chevrolet engine is equipped with automatic devices
which aid greatly in minimizing the danger of crankcase dilution.
Rapid warming up of the engine is aided by the thermo-
static water temperature control, which automatically prevents
circulation of the water in the cooling system until it reaches
a predetermined temperature.
Thermostatic heat control on the exhaust manifold, during
the warming-up period, automatically directs the hot exhaust
gases against the center of the intake manifold, greatly aiding
the proper vaporization of the fuel.
Sparing use of the choke reduces danger of raw, or
unvaporized fuel entering the combustion chamber and
leaking into the oil reservoir.
An efficient crankcase ventilating system drives off fuel
vapors and aids in the evaporization of the raw fuel and water
which may find its way into the oil reservoir .
• 75·
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