Preventive Service

a slight leak at the pump seal or in connections between

a. Causes and Effects of Leakage. The joint

pump and radiator, will allow air to be sucked into the

cooling system at high engine speeds (fig. 2-10). Air

between cylinder head and engine block actually consists

suction into the system through a perforated rubber shaft

of a large number of individual water joints at water

seal can force enough liquid out the overflow pipe to cause

transfer ports, which are all sealed by one gasket. All of

serious coolant shortage in a short period of high-speed

these joints are subjected to the strain of extreme

engine operation. Mixing air with coolant reduces heat

temperature changes within the engine, and also to

transfer and may raise temperature enough to cause

combustion pressures as high as 600 pounds per square

overheating at high engine output.

Furthermore,

inch or more. Internal leakage at the cylinder head gasket

introduction of air into the system may speed up rusting as

cannot be detected from outside inspection. Leakage of

much as 30 times and also greatly increase corrosion of all

coolant into the engine (fig. 2-11) can cause serious

cooling system metals (para 2-16c).

Clogging and

damage, especially in cold weather. Either water or

corrosion go hand-in-hand with neglected waterpump

antifreeze solution, when mixed in large quantities with

leakage and air suction.

engine oil, will form sludge which may cause lubrication

difficulties. If internal coolant leakage is not promptly

d. Preventive Service. Since results of pumping

discovered and corrected, serious engine damage can

failure, leakage of coolant, or air suction into the system

result. Even though the joint is tight enough to prevent

can be serious, water pumps require careful maintenance

liquid leakage, the slightest amount of looseness will allow

in the form of frequent inspection, periodic tightening, and

combustion gases to be blown into the cooling system (fig.

proper lubrication. Prompt detection and correction of

2-12). This can force coolant out the overflow pipe.

leakage is the most important of all water pump preventive

Burned gases dissolve in coolant to form acids which

maintenance services.

cause rapid rust formation and attack metal parts.

Figure 2-11. Coolant leakage into engine.

Figure 2-10. Points of air suction into cooling system.

2-13.

Cylinder Head Joint

2-10