Chevrolet Fleetmaster Series 1947 Owner's Manual page 50

culation of the water in the cooling system until it reaches a pre-
determined 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.
The downdraft carburetor is an aid to easy starting, thereby
minimizing the use of the choke. 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 evaporation of the raw fuel and water which may
find its way into the oil reservoir.
Control by Car Owner Under Abnormal Conditions
Ordinarily these automatic control devices will minimize, or
eliminate, the danger of crankcase dilution.
However, there are abnormal conditions of service when the
car owner must aid in the control of crankcase dilution.
Short runs in cold weather, such as city driving and excessive
idling, do not permit the thorough warming up of the engine or
the efficient operation of automatic control devices.
It
is recom-
mended that the oil be changed more often when the car is sub-
ject to this type of operation.
Poor mechanical condition of the engine, such as scored
cylinders, poor ring fit, "sloppy" or loose pistons, faulty valves
and poor ignition will increase crankcase dilution. Keep your
car in good mech{\.l1ical condition.
Poor fuels which contain portions hard to ignite and slow to
burn will increase crankcase dilution. Use good fuel.
Water in
Crankcase-Serious lubri-
cation troubles may result in cold weather due to an accumulation
of water in the oil pan. This condition is as a rule little under-
stood by the car owner. To demonstrate the chief cause of water
in the oil pan, hold a piece of cold metal near the end of the
exhaust pipe of the engine and note the rapid condensation and
collection of drops of water on it. The exhaust gases are charged
with water vapor and the moment these gases strike a cold sur-
face. they will condense, forming drops of water.