1942 - 1947 Chevrolet Shop Manual



	6-50

	proper temperature for the type anti-freeze to be used. Check the thermostat for fully OPEN and CLOSED temperatures as follows: Fully Open Place the thermostat in hot water 25° above the temperature stamped on the thermostat valve. The bellows should be completely submerged and the ■ water agitated thoroughly. Under this condition the valve should open fully. Closed Repeat the above in water 10° below the indicated temperature on the valve. Under this condition the valve should close completely. Reinstall thermostat if found OK, using a new housing gasket. 7. Fill the cooling system with proper quantity of anti-freeze and water according to instructions by manufacturer of the anti-freeze being used. NOTE—Be sure to make allowance for additional amount of anti-freeze or solution if ear is equipped with a hot water heater. 8. Warm up engine. Re-tighten all cylinder head bolts. Check radiator, water pump and all hose connections for leaks with engine hot. 9. Check and adjust valve clearance. Be sure to normalize engine prior to making this check and adjustment—Follow Instructions, "Valve Adjustment Procedure" in this Shop Manual. Lubricate all valve stems to insure free movement of the valves in the guides. Adjust the valve clearance as follows: Intake....................006" to .008" Hot Exhaust..................013" to .015" Hot NOTE—The reason for the check and adjustment of valves here even though the engine seems to perform and sound OK, is due to the fact that the cylinder head bolts have been tightened— this decreases the valve clearance and may cause the valves to hold open and not only result in a very unsatisfactory performing engine but may burn and warp the valves and cause expense to the owner. CARE OF THE COOLING SYSTEM Every car and truck requires periodic cooling system service. Seasonal changes make this service very important due to the use of anti-freeze solutions. In many instances this service consists of draining and refilling the cooling system only. However, this does not properly prepare the system for continued efficient operation.	During the winter months the cooling system accumulates rust and corrosion in the radiator from the engine water jackets, forming a scale which if not removed will eventually clog the water passages, resulting in inefficient operation of the cooling system vitally affecting engine performance and economy of operation. Rust in the cooling system is caused by oxygen in the water which has a corrosive action on iron and steel. Oxygen enters the cooling system through the overflow pipe. Since oxygen is the main factor in causing corrosion, it is necessary to reduce the amount entering the system. We cannot control the amount of oxygen in the water but we can control the amount entering the system in other ways. Figure 103 shows how rust accumulates in the water passages.

		Fig. 103—Cross-Section Showing Rust Accumulation in Water Passages Another common cause of corrosion is a loose cylinder head or damaged gasket, which allows exhaust gases to be blown into the cooling system. As these gases contain strong acids corrosion is produced in the cooling system. As this corrosion builds up in the system the result is blocked or reduced circulation and overheated engine, which may cause burned valves, cracked cylinder head, scored pistons and cylinders, necessitating major motor repairs. The facts presented prove that attention must be given to the engine cooling system to keep it in efficient operating condition. For this reason, cooling system service is recommended and must be closely followed to obtain the desired results. The two operations required for this service are: First—Cleaning and reverse flushing Second—Reconditioning the system