METAL BODY REPAIR - OD1653 - LESSON 2/TASK 2
(4) Field Test Task. A field test tank consists of a one piece canvas
bag with wooden staves in pockets to hold the sides up, and four round poles
running through canvas loops to support the rim. A rubber mat protects the
bottom of the tank from being torn by the radiator. When the tank is
collapsed, two poles are removed and placed inside the tank, which is then
rolled inside the mat and fastened with five flat metal hooks.
(5) Locating Leaks. Locating the leaks when bubbles rise is often
difficult. Raise the radiator in the tank until the source of the bubbles
is at the surface of the water. Locate as many large leaks as possible,
drawing upon the knowledge of radiator construction; quite frequently the
large ones can be detected more easily at a lower pressure. Repair these
and retest for smaller ones. If water leaks in and remains for a later
test, it may seal the compressed air and prevent it from escaping, and thus
cause leaks in the bottom to remain undiscovered. Then on the last test,
turn the radiator over in the tank.
(a) Two leaks occurring exactly opposite one another, one near the
front of the core and the other at the back, should not be confusing. If
testing a honeycomb core, stand it on edge, allowing the bubbles to come up
the face. A tubular core should be raised until only the lower rows of
tubes are immersed in the water. An accurate idea of the location of leaks
is based upon a thorough understanding of core construction. To locate open
seams at the back of a tube, use a sharp pointed tool.
(b) To find very small leaks, place the bench light in back of the
radiator so that the interior of the core can be seen. Stand the radiator
on the bench and spread the supposed leak with flux or soapy water from an
eyedropper, oilcan, acid brush, or swab. Compressed air seeping through the
leak will cause the liquid to foam.
(c) As heavy truck cores occasionally come to the shop with water
tanks removed, the water passages or tubes may have to be closed before
tests can be started. For a honeycomb core, solder dummy tanks to the
header strips. These may be made of discarded tanks or plate metal, to one