Troublesome leaks some times occur in places where it is very inconvenient to disassemble the parts, plug the openings, and to subject them to air pressure when submerged in water. Among the parts where such trouble arises are fuel lines, gasoline air pressure lines, acetylene lines, etc.

To locate such leaks, make up a strong solution of soap flakes in warm water, and brush the suds onto the item in question. With the soap suds, even such low air pressure as can be cause by blowing with the mouth through the assembly will cause large bubbles to appear at the point of leakage. Be careful not to get the soap all over the body paint, and if you do, be sure to wash it off thoroughly at once, and dry with a soft cloth.  

Antique Automobile
1946