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Cooling System Servicing and Troubles


To ensure that the engine cooling system will operate normally, one should observe the following rules.

Fill the cooling system only with clean, preferably soft water. Soft water can be recognized by its ability to form an immediate lather with soap. It is recommended that use should be made of the water which has been already used in and drained from the system, for it contains less calcium salts. Hard water can be softened by boiling during 30 min and also by addition of washing soda (sodium carbonate) or trisodium phosphate (1 to 2 g per liter of hot water, depending on its hardness).

Fill the radiator to the level of the filler neck and never allow the coolant level to drop more than 8 cm below the filler neck.

If necessary, top up the coolant level of an overheated engine only gradually, keeping the engine running without fail. In winter time, do not use excessively hot water to fill the cooling system of a cold engine, because the sharp change in temperature may cause the cylinder head and block to crack.

Never operate the engine with the water temperature in the radiator exceeding 100°C.

Do not fail to check regularly, every shift, the water level in the radiator. When doing this, remove the radiator pressure cap with care, so as not to get your face and hands burned by the hot water and steam that may erupt from the filler neck. Should the water level in the radiator prove too low, top it up and check the system for possible leaks. An excessive water leakage from the drain hole in the water pump body indicates that the pump seal assembly components have worn out and must be replaced. If there are no water leaks, but the engine consumes too much water, check the condition of the radiator pressure cap.

every 60 hours of operation lubricate the water pump bearings. To do this, clean the lubricator, fit the nipple of a grease gun to it, and pump the gun three or four times. Check the fan belt tension. The belt is considered to be tightened properly if it flexes 10 to 15 mm (15 to 20 mm in air-cooled engines) when a load of 30 to 40 N is applied to it midway between the crankshaft and fan pulleys. Use a drive-belt tension gauge to make the check. The fan belt tension is adjusted by changing the position of the generator or fan-belt tightener.

Remember that too tight a fan belt causes the bearings to wear out prematurely, while a slack belt causes the engine to overheat and wears off intensively.

Lubricant-contaminated belts should be cleaned with a wiping rag soaked with gasoline.

every 960 hours of operation clean the cooling system with a special solution (e.g., 100 g of washing soda and 50 g of kerosene per liter of water) to remove scale. To do this, drain the system, fill it with the solution, and operate the engine for a full shift. Then drain the solution from the system and flush the system with clean water.

When servicing an air-cooled engine, clean the protective screen of the air blower and the cooling fins of the cylinder barrels and heads.

WHEN CARRYING OUT THE SEASONAL servicing procedures, test the thermostat and the coolant temperature gauge.

To test the thermostat, remove it from its housing, immerse in a container of water, and heat the water. At a temperature of 70°C the main valve should start to open, and when the water temperature reaches 85°C, the valve should be fully open. The full stroke of the valve should be around 9 mm. If the thermostat fails to open at the specified temperature, or if it fails to open to its maximum, it must be replaced.

To test the temperature gauge, check its readings against the readings of a mercury thermometer immersed in the radiator filler neck. Should the readings of the gauge be at variance with those of the thermometer, the gauge or its sending unit must be replaced.

Cooling system troubles usually manifest themselves in engine overheating. The causes of overheating may be the following: lack of coolant in the cooling system, closed radiator shutter or blind, scale and sludge accu­mulations in the cooling system, too loose or soiled fan belt, engine overload, faulty thermostat, and in some engines, broken lock pin of the water pump impeller.

In cold weather, water may freeze in the engine cooling system, thus stopping coolant circulation. Some parts of the engine will overheat if not cooled, and this could seriously damage the engine. What is worse, water expands when it freezes. Water freezing in the cylinder block could expand enough to actually crack the block. Water freezing in the radiator could burst the radiator tanks and tubes. Therefore, under such conditions, water must be drained from the cooling system whenever the engine is stopped for any prolonged period of time, or an antifreeze solution must be used to fill the system.

Lately, the antifreeze solution has been recommended for use as a coolant. It should be used year-round in the engine cooling system and changed every two years. Keep in mind that the antifreeze is very toxic and will cause poisoning if ingested. Therefore, do not fail to wear rubber gloves when pouring the antifreeze solution, never use your breath to pull it into a siphon hose, and neither smoke nor eat when handling the solution in any way.

The causes of overheating of air-cooled engines may be a slack, contaminated, or worn fan belt, a clogged protective screen of the air blower, or clogged airways between the cooling fins of the cylinder barrels and heads.


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