Chevrolet Light - Page 77

accumulates it sho uld be removed by draining th e crankcase
as frequently as may be required.
It is always advisab le to let the engine reach norma l operat-
ing temper ature be f ore draining the crankcase. Th e benefit of
draining is, to a l arge ex t en t, lost if the crankcase is drained
when the engine is cold as some of the suspen d ed foreign ma-
terial will cli ng to the sides of the oil pan and will not drain
ouVread ily with the sl ower moving oi l.
Crankcase Dilution
P robably the most serious phase of engine oil deterio r a-
tion is that of crankcase dilution, which is the thinning of
the oil by fuel vapors l eaking 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" period, wh en the fue l is not
th orough ly vaporized and burned .
Aut o mati c Co ntrol D ev ices to Minimize Crankc ase Diluti On.
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 contro l, which automatically prevents
circulation of th e water in the cooling system until it reaches
a predetermined temperature.
Thermostatic heat contro l on the exhaust manifold, during
the warming-up period, automatically directs the hot exhaust
gases against the ce nt er of the in t ake manif old , grea tl y aiding
the proper vapor.i.zation 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 cran kcase vent il ating system dri ves off fuel
vapors and aids in the evaporization of the raw fuel and wat er
which
may find its way into the oil reservoir.
Co nt ro l by Tru ck Owner Und er Abnorm al Conditions. Ordi-
narily the above au tomatic control devices will minimize, or
eliminate, the danger of crankcase dilution.
However, there are abnormal conditions of service when
the truck owner must aid in the control of crankcase dilut ion.
Short runs in cold weather, such as city driving and
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