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8
Chapter I-General Engine Repair
carburetor float. Check the condition of the needle and
seat. Replace if necessary.
(c) Check fuel pump pressure. If the pressure is
excessive, the pump was forcing fuel past the float
needle and should be rebuilt or replaced.
c. Cooling System.
The cooling system is thermostatically controlled to
regulate engine operating temperature and provide for
a short engine warm-up period.
(1) ENGINE OVERHEATS. Usually, engine over-
heating is the result of insufficient coolant supply. Check
the coolant first. Make certain that the cause of trouble
is not anti-freeze evaporation.
(a) If the supply is low, check for leaks in the cooling
system, make repairs as necessary.
(b) Check the water pump belt for proper tension
and adjust it if it is loose.
(c) Inspect the radiator fins for obstructions (bugs,
dirt, etc.). Clean it if it is clogged.
(d) Using a thermometer in the radiator, check the
gauge reading for accuracy.
NOTE: Inaccurate readings are sometimes caused by
insufficient clearance IJetween the head cas ling and
the temperature sending unit element. Repair or re-
place as necessary.
( e) Check the thermostat for proper operation and
heat range. If defective or of the wrong heat range,
replace the thermostat.
(f) Check the ignition timing and adjust if necessary.
(g) Check the radiator for proper flow. Flush the
radiator if necessary.
(h) Remove the water pump and check for a defec-
tive impeller or water passage obstruction. Repair or
replace as necessary.
(2) ENGINE FAILS TO REACH NORMAL OPER-
ATING TEMPERATURE.
Generally, this symptom
i~
caused by the thermostat
sticking or being of the wrong heat range. Check the
thermostat first. If the engine still does not reach operat-
ing temperature, check the gauge and sending unit,
with a thermometer in the radiator, for accuracy. Re-
place the defective unit.
2. ENGINE TUNE-UP
During the life of an automotive vehicle, it should
receive regular maintenance and inspection services. In
addition, to maintain satisfactory performance, an en-
gine tune-up should be performed periodically.
Any type of engine test equipment may be used to
make the tests outlined in the checking procedures. As
the checks are performed, make a visual inspection of
the wiring, vacuum hose, cooling system hose, heater
hoses, etc.
a. Minor Tune-Up.
A minor tune-up consists of the following operations:
(1) INSPECT
IGNITION
WIRES,
BATTERY
CABI.lES, AND CHECK THE CONDITION
OF
THE
BATTERY. Inspect all ignition cables for worn or
damaged insulation. Make sure that the spark plug
wires are firmly seated in the distributor cap and that
the terminals and the terminal sockets are free from
corrosion.
Inspect the battery case for cracks and leaks. Check
the water level in the battery. Inspect the battery cable
connections for corrosion and clean if necessary. Brush
the cable connectors with grease to retard further cor-
rosion, then tighten them.
(2) TEST CYLINDER COMPRESSION. Operate
the engine until normal operating temperature is
reached. Turn the ignition switch off. Remove all spark
plugs. Set the throttle to wide open position and leave
it open for the test. Using a compression tester, test the
compression of each cylinder. Crank the engine for at
least four compression strokes. Note the reading on the
first full stroke as well as on the final stroke to deter-
mine if any variation exists. All cylinders should be
tested the same number of strokes to assure accurate
readings.
The compression of all cylinders should be uniform
within ten pounds. Record the compression of each cyl-
inder to indicate to the customer the internal condition
of his engine.
A reading of more than ten pounds above normal in-
dicates carbon or lead deposits in the cylinder.
A reading below normal indicates leakage at the rings,
valves, or gasket.
(3) CLEAN,
ADJUST,
AND INSTALL SPARK
PLUGS. Sandblast the spark plugs, wipe the porcelain
clean, file the electrode tips flat and adjust the spark
gap. Test the plugs in an approved spark plug tester.
Replace any plugs that have broken or chipped porce-
lain, badly burned electrodes, or that do not check satis-
factorily on the tester. Install the spark plugs and
tighten them to the specified torque.
(4) CHECK AND ADJUST TIMING AND IN-
SPECT BREAKER POINTS. Disconnect the vacuum
line between the distributor and carburetor. Start the
engine and operate it at idle speed. Check the timing
with a timing light and make the necessary adjustments.
Connect the distributor vacuum line after completing
the adjustments and check ignition advance as the en-
gine is accelerated. Inspect the distributor points for
pits, excessive metal transfer, and bums. Replace points
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