Figure 4-35. Belt Tension Adjustment

TM 10-3930-633-12

indicate previous radiator leakage. These spots

away from the engine until belt tension is firm.

may not be damp if water only or methyl-alcohol-

Then tighten the alternator mounting bolts and

base anti-freeze is in the cooling system since

check the tension as indicated above. Reset the

such coolants evaporate readily. An ethylene-

alternator as necessary for correct belt tension.

glycol-base antifreeze shows up existing leaks as

Finally, torque the alternator mounting bolts 25

it does not evaporate.

to 35 ft/lb.

c. Radiator Flushing.

(1) It is recommended when using water for

coolant that the cooling system be flushed and

checked for leaks twice a year, preferably in the

fall before antifreeze is added and in the spring

when the antifreeze is drained.

(2) Reverse flushing will aid greatly in

removing rust and scale, especially when used

with a flushing solution. A cleaning solution

should be used to loosen the rust and scale before

reverse flushing the cooling system.

(3) Flushing is accomplished through the

system in a direction opposite to the normal

coolant flow. This action causes the water to get

behind the corrosion deposits and force them out.

Continue this flushing operation until the water

runs clear through the top hose.

d. Radiator Removal. Refer to figure 4-33 and

proceed as follows:

Figure 4-35. Belt Tension Adjustment

(1) Remove the engine cooling fan from the

4-67. Radiator

fan hub on the water pump shaft.

a. General Maintenance and Inspection.

(2) Drain the cooling system.

Maintenance of the radiator consists of keeping

(3) Disconnect the upper and lower radiator

the exterior of the radiator core clean, the interior

hoses from the radiator.

free from rust and scale, and the radiator free

(4) Disconnect the transmission oil cooler

from leaks. Check the cooling system fluid level

lines at the bottom radiator tank. Plug trans-

and for leaks each 100 operating hours. The

mission oil cooler ports in the radiator im-

exterior of the radiator core should be cleaned and

mediately to prevent system contamination.

the radiator inspected for leaks each 100 hours of

(5) Remove bolts (14), washers (17), nuts

normal service of the vehicle. Cleaning should be

(15), rubber mounts (16), and remove radiator

performed by blowing out with air stream or

from the vehicle.

water stream directed from the rear of the

e. Testing Radiator for Leakage.

radiator. Visual inspection is not sufficient as the

(1) With radiator removed from vehicle,

accumulation of small particles of foreign material

install radiator cap and block or plug the upper

on core surfaces can restrict cooling without

and lower radiator hose connections.

closing the core openings.

(2) Remove the drain cock and connect an air

b. Radiator Leakage. Radiator leakage oc-

line with an air pressure gage to the drain cock

casionally results from corrosion perforation of

port.

the metal but most leakage results from

(3) Submerge the radiator in a tank of water.

mechanical failure of soldered joints when too

Open the air line to the radiator and apply a

much strain has been put on the joint. Fractures

pressure of not more than 12 to 15 PSI.

occur most often at the joint where the radiator

(4) Watch the radiator for signs of bubbles

inlet and outlet pipes are attached to the tanks.

coming from the core during this pressure test.

When the seams break, the entire soldered joint is

The pressure cap should open at 12 to 15 PSI.

exposed and can corrode, but breakage rather

Shut off the air to the radiator and allow the air to

than corrosion is the primary cause of seam

escape until the safety cap seats. Hold the

leakage, Examine the radiator carefully for leaks

pressure for 5 minutes. If no bubbles appear from

before and after cleaning. Cleaning may uncover

the core, the radiator is good. If bubbles appear,

points of leakage already existing but plugged

mark the origins of the bubbles and remove the

with rust. White, rusty, or colored leakage stains

4-54