Figure 2-8. Points of leakage in packless-type pump seal.

Figure 2-7. Corrosion of water pump impeller.

CAUTION

Operation of engine with coolant frozen may shear

off the impeller pin and leave impeller loose on

shaft, or cause slippage of pump belt drive that

would burn belt at the driving pulley.

Figure 2-8. Points of leakage in packless-type pump seal.

b. Leakage (figs 2-8, 2-9) Leakage is a more

common trouble than pumping failure. The pump housing

joint is under strain from the pump drive and may cork

loose and leak if the mounting bolts are not kept tight. The

water pump shaft and seal assembly forms the only

moving water joint in the cooling system (para 1-13b). In

the adjustable gland-type pump, normal near of packing

will allow leakage unless gland is tightened periodically

and packing replaced when worn. Shaft and bearing will

be damaged if packing gland is too tight. In newer

packless-type pumps (para 1-13d), the self-adjusting seals

are subject to wear, deterioration, and leakage. Thrust

seal washers and seats are prematurely worn by abrasive

action of sand, dirt, and rust in coolant and by operation

with engine overheating. Bearing and shaft damage,

which leads to leakage and pump failure, can result from

neglect of lubrication in pumps that require it. But over-

lubrication, especially with a high pressure gun, forces

grease into the cooling system, which contributes to

clogging and overheating.

Figure 2-9. Leakage in adjustable gland-type pump seal.

c. Effects of Failures and Leakage. Forced coolant

circulation is so necessary in the modern cooling system

that any reduction in pumping capacity causes a loss of

cooling effectiveness.

Complete pumping failure is

invariably followed by sudden overheating and operating

difficulties. Loss of coolant is not the only, trouble that can

result from a water pump leak. Coolant leakage at the

shaft, if not properly corrected, will destroy lubrication and

cause corrosion and wear of shaft and bearings. Even

2-9