Repairing Tubes

strengthens the weakened area. A patch usually results in

3-34.

Repairing Tubes

a repair sufficient strength to prevent recurrence of the

crack. When a header is cracked between tubes, a

a. General. Small leaks may be repaired by sealing

noticed patch may be used. Cracks that are located on a

with solder. Sealing large leaks with solder will only result

multiple contoured surface are usually brazed or silver

in filling or plugging the tube. When large leak is pinched

soldered.

to prevent solder from plugging the tube, water flow

b. Patch Repair

through the tube is restricted.

Therefore, it is

(1) Cleaning the area with alternate use of heat

recommended that only small leaks be repaired by sealing

and muriatic acid is usually sufficient. For more difficult

with solder. This type of repair consists of gaining access

cleaning, use wire brush and muriactic acid. On extremely

to the leak, cleaning, tinning and soldering.

difficult multiple-contoured surfaces, abrasive blasting may

b. Sealing Tube Leaks With Solder'

be required.

(1) Heat the tube in area to be repaired. Move

(2) Tin an area at least 1 inch larger than all

or spread fins slightly to gain access to the leak.

points of the crack. Cut a patch from 16 oz copper sheet

(2) Heat the tube around the leaking area and

(this material is approximately 021 inches thick) to a size

brush on muriactic acid. Repeat this several times to

that covers the tinned area. Tin both sides of the copper

clean the repair area.

patch.

(3) Heat the tube and apply flux and tinning

(3) Check fit and size of copper patch by

mixture.

placing it over the crack. Be sure that it is formed to the

(4) When the area is completely tinned, heat

surface contour and covers the crack with the surface

and flow solder to cover the leak.

contour and covers the crack with the proper overlap.

(5) Restore fins to their original position by

Remove patch and position radiator so that repair surface

using duck bill pliers.

is level.

(6) Test with required air pressure.

(4) Heat and apply a thin layer of solder over

the crack and tinned area.

3-35.

Blocking Tubes

(5) Position patch, heat and flow additional

solder around edges of patch and cool with water.

Most radiators are designed with an overload capacity.

(6) Wash patched area thoroughly and leak test

When tubes are blocked or plugged, the overload capacity

it proper air pressure Figure 3-25 illustrates a tank patch

is decreased in proportion to the number of tubes blocked.

repair and Figure 3-26 shows a header repair using a

Blocking of tubes is more economical than replacing or

notched patch. (Before soldering ).

splicing. A limited number may be blocked in most

applications. Radiator cores in tactical wheel vehicles (3/4

ton through 10 ton trucks) with not more than two tubes

blocked are acceptable, except M39A2 series trucks,

which must have all tubes functioning. If a tube is split

lengthwise or severely damaged, it may be blocked at

each end. When a tube is damaged along its length in a

large area, it can be disconnected from the headers and

both header holes filled with solder. Tubes can also be

blocked by punching a hole approximately 2 inches from

each end. Flare the holes, clean, tin and fill with solder.

3-36.

Patching Headers and Tanks

a. General. Cracks occur in headers and tanks

from temperature and pressure changes. Other ruses are

mechanical stresses and vibrations during normal

operation. These cracks, if repaired by lder alone are

likely to recur. Solder alone contributes very little to

Figure 3-25. Tank patch repair (before soldering).

structural rigidity and strength a copper patch (a thin patch

cut from 16 oz copper let) is soldered over a crack, the

bonding area of solder is greatly increased.

This

3-18