Figure 2-5. Radiator caps, plain

Figure 2-5. Radiator caps, plain - and pressure-type.

b. Causes of Failure The radiator cap is subjected

steam that might cause personal injury.

to high coolant temperature which cause relatively rapid

d. Handling and Maintenance To avoid damage to

deterioration of the gasket. The valves and underside of

cap gasket and gasket seat on filler neck, care should be

the cap are exposed to extremely corrosive effects of hot

exercised in removing and replacing cap. When filling

steam and air in the upper radiator tank. Since the cap is

radiator, metal filling spouts or nozzles should not be

located above normal liquid level, it receives little

allowed to come in contact with filler neck gasket seat.

protection from rust inhibitors in the coolant (para 2-32),

Proper maintenance consists of daily inspection of gap,

with the result that cap and valves may fall from corrosion

seat, and gasket, and periodic cleaning of cap and valves,

damage. Even a small amount of rust scale or dirt will

checking of valve operation, and testing for tightness of

interfere with operation of pressure and vacuum valves.

valves and cap seal (2, fig. 2-1).

Frequent removal and replacement of radiator cap for

coolant level observation increases the possibility of

leakage and pressure loss, due to wear of gasket and cap-

2-10.

Radiator

locking mechanism.

a. Leakage and Failure (fig 2-6) Engine vibration

c. Effects of Failure An air leak above liquid level in

and road shocks put a strain on all radiator seams and

the radiator, such as at cap gasket or pressure valve, will

joints that may lead to breakage and leakage, particularly

prevent pressure from building up, and benefits of the

in water tubes, tanks, and outlet and inlet fittings.

pressure cap will be lost. Coolant may boil in some

Additional strain is set up by extreme changes In metal

cooling systems even at normal operating temperatures if

temperatures, especially during cold-weather operation.

the cap is not pressure-tight. If the pressure valve fails to

Cross-country driving over rough terrain multiplies the

open, sufficient pressure may build up in the system to

effects of ordinary shock and vibration. Neglect of small

break radiator seams or blow off hose connections.

leaks may result in complete radiator failure, excessive

Failure of vacuum valve to open when system cools may

leakage, rust clogging, and over-heating difficulties. Thus,

cause collapse of hose and other parts which have no

it is extremely important to keep the radiator mounting

internal support.

properly adjusted and tight at all times, and to detect and

correct promptly even the smallest leaks.

WARNING

The radiator cap should be turned to the "vent"

position before removing, to allow escape of hot

2-7