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.

One of 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 Finder
1068 Powder (Gray) 25 lb. Can

Other causes of internal leaks are:

1. Distorted cylinder heads and blocks. These should be checked with a straight edge and resurfaced if necessary.
2. Improper torquing of cylinder heads. A reliable torque wrench must be used and engine manufacturers recommended sequence and ft/lbs torque used.
3. Faulty or blown head gasket. This is usually caused by a distorted head or block or improper torquing.
4. 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.

1. Drain used oil while engine is warm and discard oil.
2. Remove oil filter cartridge and replace with new one.
3. Fill crankcase to proper operating level with a mixture of three parts SAE 1OW engine oil and two parts butyl cellosolve.
4. 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 damage.
5. Stop engine and immediately drain solution from crankcase.
6. Refill crankcase with flushing oil or SAE 1OW engine oil. Run engine at fast idle for 10 to 15 minutes and again drain crankcase.
7. Install new filter cartridge.
8. Refill crankcase with fresh engine oil. Follow viscosity index and type oil recommended by engine manufacturer.

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!

(P35-36)

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