Service and Repair Manual

pounds to the inside of the cooler and using oxyacetylene flame, apply heat carefully to the dent, allowing the heating of the metal with its consequent decrease in hardness to form out to the proper radius under the action of air pressure on the inside. Sharp dents can sometimes be pulled out by soldering the end of the silver solder wire to the point of the dent and pulling the shell into position.

     (8) Bullet Holes in Shell. - Small holes, that is, anything corresponding to 1/4 inch in diameter or under, may be patched using a piece of .040-inch or .050-inch thick brass and soft soldering over the hole. Large holes in the shell may be repaired by silver soldering provided the core is properly protected from excessive heating by the use of wet cloths. Holes in the inside shell are extremely difficult to repair and it is doubtful ill the cooler can be salvaged in such cases. These remarks in regard to the holes in the cooler and the repair thereof apply only to the holes in the outside shell. However, in the hands of a skillful workman it is quite possible that bullet holes in the inside shell can be repaired. This will require considerable familiarity with cooler construction and repair work and is not recommended.

     (9) Bullet Holes ln Core. - If a large portion of the core has been damaged, that damaged section may be removed by using an oxyacetylene torch as previously described under ÒCollapsedTubesÓ and ÒTube Leaks".

     j. Cleaning After Repair,

     (1) Oil Cooler. - After repairing and testing, any cooler should be thoroughly flushed inside and out with hot water and steamed as specified in this section, paragraph 2.f.(1). However, any steaming operation may be omitted in case the cooler is to be installed for immediate use, but in this case it will be first thoroughly dried either by immersing in hot oil,

as outlined below or by baking it in an oven at a temperature from 121° to l35°C (250° to 275°F) for approximately 1 hour, or until all evidence of moisture has been removed. If the regulator is to be placed in stock, apply the hot oil treatment td remove the moisture and cover the internal surfaces with a protective coating. This is accomplished by completely immersing the cooler in a tank of clean, light engine oil, approximately SAE 20, maintained at a temperature of 121°C (250°F) plus or minus l0°. The cooler should be agitated thoroughly until all bubbling ceases, which will indicate that the water is evaporated and the interior of the cooler is completely coated. It should then be drained and the openings closed for storage.

     (2) Coolant Radiator. - After repairing and testing, any radiator should be thoroughly flushed inside and out with hot running water and steamed as specified in this section, paragraph 2.¤ (2). However, any steaming operation may be omitted in case the radiator is to be installed for immediate use.

     k. Fuel, Oil, and Hydraulic Tubes. - The copper and aluminum tubes of the fuel, oil and hydraulic systems must be replaced if damaged in any way with the same type tubes as originally used.

     l. Fuel System - Self-sealing Lines (Tubes). - On the P~40 airplane, AK-721 and subsequent, all fuel lines are gummier protected self-sealing tubes. These lines are made up of a seamless compounded inner tube, layers of self-sealing material, plies of reinforcement and a compound cover. The hose will seal completely within 4 minutes after damage at a temperature of -20°F (-29°C). These lines must be replaced if damaged in any way with the same type tubes as originally used. Care must be exercised when tightening clamps that they are not too tight, because the outer compound cover may be pierced and thus damage the tube.