METAL BODY REPAIR - OD1653 - LESSON 2/TASK 2
(1) Visual Inspection. Deposits of line or magnesia left on the outside
surfaces by evaporating water indicate leaks in a radiator. Before removing
a bad radiator from a vehicle, inspect it for these deposits to determine
the amount of repair needed. Experience will teach how to determine the
true condition of a radiator from observation. There are at least as many
leaks as can be seen. Do not make an air or water test until all the leaks
indicated by visual inspection have been repaired, because the effectiveness
of these tests in discovering hidden leaks is lost when they reveal obvious
(2) Air rest. The air test, so called because leaks are indicated by
escaping air, is the most efficient means of locating hidden leaks. Connect
an air pressure tube directly or by a nipple to the bottom of the overflow
pipe. Screw the cap tightly on the filler neck and plug the inlet and
outlet with expanding or cupshaped rubber stoppers. Immerse the radiator
in a testing tank, release the air, and trace the bubbles to their source.
(a) The most practical pressure for testing is three pounds per
square inch (psi) above normal operating pressure. Greater pressures will
damage the delicate construction of radiator cores. Frequently, leaks will
appear at low pressure but not at high pressure, which closes the joints
with accumulated lime and magnesia deposits or with expanded metal.
(b) The air pressure system used by garages for tire inflation,
consisting of a compressor, motor, pressure tank, gages, and reducing
valves, is very satisfactory for radiator testing when the work is enough to
keep several men busy. When no compressor is available, an ordinary tire
pump will supply enough air pressure.
(3) Testing Bench. Since testing is a dirty job, arrange the shop
equipment systematically to minimize disorder. The testing bench should be
placed near an air pressure source and water lines, preferably endwise to a
wall under or just back of a window, to light the radiator adequately.
Prevent damaging the radiator by excessive air pressure by using an air