high efficiency, automotive engines are designed to operate
with a pressurized cooling system, or a certain pounds per square
inch pressure. As horsepower and engine efficiency were increased
the engines developed more heat and the car manufacturers, because
of body design, decreased the size of the radiator. To properly
cool the engine it was necessary to pressurize the cooling system,
which raised the boiling point of the cooling water.
The system is pressurized by using
a spring loaded radiator cap and the spring is made to maintain
a certain tension, or pressure. A vacuum relief valve is incorporated
into the radiator cap to prevent collapse of the radiator
when the system cools (see Fig. 1).
If the cooling system pressure builds
above the design limit of the cap, the spring allows a relief
valve to open and relieve the pressure. If the spring loses
its tension, partially or completely, the pressure of the
cooling system will be lowered from design limits, water will
boil away and the engine will run at high temperature. This
is especially true if the car is air conditioned. The radiator
cap should be tested every six months, or ten thousand miles,
to be sure the cooling system is operating at the temperature
for which it was designed.
Atmospheric pressure at sea level is
14.6959, or approximately 14.7 pounds, per square inch and
the boiling point of water at sea level is 2120 Fahrenheit.
If the cooling system is designed to operate at 15 pounds
pressure, or with a 15 pound pressure cap, the system would
operate at approximately 29.7 pounds and the water would boil
at 249.37 OF. If the pressure cap lost its tension, the cooling
system pressure would be lowered and the water would boil
at a correspondingly lower degree. This will cause loss of
water and could cause serious damage from overheating.
INTERNAL COOLANT LEAKS
Internal coolant leaks
is one of the most serious problems in the automotive industry
and can result in costly engine damage in a very short time
if coolant loss is not detected and corrected. This has always
been a problem with liquid cooled engines and has become even
more serious since the advent of permanent type anti-freeze,
or ethylene glycol base anti-freeze.
the most common causes of internal coolant leaks is cracked
cylinder heads and blocks. These cracks can be overlooked when
a. visual inspection is made. The only sure way these cracks
can be located and their length determined is by the use of
a magnetic crack finder. See photo below.
1033 Hastings Crack
1068 Powder (Gray) 25 lb. Can
Other causes of internal leaks are:
Distorted cylinder heads and blocks.
These should be checked with a straight edge and resurfaced
Improper torquing of cylinder heads.
A reliable torque wrench must be used and engine manufacturers
recommended sequence and ft/lbs torque used.
Faulty or blown head gasket. This
is usually caused by a distorted head or block or improper
Cracked or damaged water cooled
valve guides (where used). These guides should be checked
for cracks or defects.
When ethylene glycol anti-freeze leaks
into an engine it will contaminate the engine oil and cause
hard starting in both hot and cold engines. In some cases
the engine can be contaminated to the point where the moving
parts "freeze" together. In case of ethylene glycol
contamination the following procedure should be followed.
Drain used oil while engine is warm
and discard oil.
Remove oil filter cartridge and
replace with new one.
Fill crankcase to proper operating
level with a mixture of three parts SAE 1OW engine oil and
two parts butyl cellosolve.
Run engine at fast idle for 20 to
30 minutes. The oil pressure should remain constant, the
water temperature should be above 1500 F., but not exceed
normal operating temperature. This is extremely important
and must be watched carefully to prevent possible engine
Stop engine and immediately drain
solution from crankcase.
Refill crankcase with flushing oil
or SAE 1OW engine oil. Run engine at fast idle for 10 to
15 minutes and again drain crankcase.
Install new filter cartridge.
Refill crankcase with fresh engine
oil. Follow viscosity index and type oil recommended by
NOTE: In some cases it may be necessary
to repeat above instructions. This will depend on length of
time and extent of contamination. If the engine has seized,
remove the spark plugs and pour butyl cellosolve in each cylinder
in enough quantity to cover the piston. The amount of coolant
damage in the engine will determine how long to soak before
engine can be turned over. In severe cases if engine remains
stiff it may be necessary to tear the engine down and individually
clean each part with soap and water.
Butyl cellosolve is used as a paint
and varnish solvent and in some areas can be purchased from
the local paint distributor. It can also be obtained from
Carbide and Chemicals Company, a division of Union Carbide
and Carbon Company, other chemical companies in your locality,
or oil companies who deal in solvent products. Oldsmobile
dealers list this product under part number 576046.
CAUTION: Butyl cellosolve should be
handled with extreme care because it is toxic, inflammable,
explosive and will damage car finishes. HANDLE WITH CARE!