Water Pump - TM-750-2540014

1-13.

Water Pump

a. General. Every modern cooling system has a

water pump to circulate the coolant in the system. The

pump, which is usually located on the front or side of the

engine block, receives coolant from the bottom of the

radiator and forces it through the water jacket into the

radiator top tank.

b. General Construction The water pump is a

centrifugal-type pump, having an impeller with blades

which force the coolant outward as the impeller rotates.

The impeller is located in a pump housing and is mounted

on a shaft which runs on one or more bearings. The shaft

is driven by the engine through a belt or a shaft (para 1-5).

The fact that the impeller is submerged in the coolant but

must be driven from outside of the cooling system, creates

the problem of sealing the impeller shaft against leakage.

The water pump shaft seal is the only moving water joint in

the cooling system.

c. Packless Type. The most commonly used type

of pump on military vehicles is the nonadjustable packless

type. The packless pump has a built-in, self-adjusting

Figure 1-10. Liquid and gas joints in cylinder head gasket.

seal. Individual pumps vary somewhat in seal materials

and arrangement of assembly. Some packless pumps are

1-15.

Engine Water Jacket

prelubricated when assembled, but others require periodic

lubrication.

a. Construction The water passages in the cylinder

block and cylinder head form the engine water jacket In

1-14.

Cylinder Head Joint

the cylinder block, the water jacket completely surrounds

all cylinders along their full length. Within the jacket,

a. Water Transfer Ports. The coolant flows from

narrow water passages are provided between cylinders for

cylinder block up into cylinder head through passages

coolant circulation around them.

In addition, water

called water transfer ports The lower part of each passage

passages are provided around the valve seats and other

is in the block, and the upper parts is In the head. A tight

hot parts of the cylinder block. In the cylinder head, the

seal in the joint between the two parts of these water

water jacket covers the combustion chambers at the top of

passages is very important.

the cylinders and contains water passages around the

valve seats when the valves are located in the head.

b. Cylinder Head Gasket (fig 1-10) The joints in the

numerous water transfer ports, as well as the combustion

b. Function and Operation (fig. 1-11). Passages of

chamber joints, are all sealed with one large gasket called

the water jacket are designed to control circulation of

the cylinder head gasket. To obtain the tightest possible

coolant and provide proper cooling throughout the engine.

seal in these joints, the openings in the gasket, which

Waste heat flows directly to the coolant through metal

match the water transfer ports and combustion chamber

walls of the combustion chambers and cylinders. Heat

openings, are reinforced with metal eyelets described as

absorbed by the pistons passes into the coolant by way of

grommets. The head gasket has a double duty to

the cylinder wall. The heat in the valves flows to the

perform; it must seal the extreme pressures of combustion

coolant through the valve seats and guides. Since

within the cylinders and at the same time maintain

exhaust valves may run as hot as 2,000F (yellow-red

leakproof coolant joints at the water transfer ports. To be

heat), proper cooling around the exhaust valve seat is of

specific, the cylinder head gasket must prevent

special Importance.

combustion gas leakage to the outside of the engine,

between cylinders, and into the water passages, it must

also prevent coolant leakage outside the engine, and to

the cylinders of the engine. Proper uniform tightness of

the cylinder head bolts is necessary to maintain a

leakproof

head

gasket

joint.

1-8