Method of unblocking an obstructed cooling passage

A method of repairing a gas turbine component from which a previous coating has been removed from a first surface and which has a wall having oppositely facing first and second surfaces and a plurality of passages within said wall with said passages each having opposite ends terminating at the first and second surfaces and a new coating to be applied to the first surface from which the previous coating has been removed, the method comprising:

• a) applying the new coating to a region of the first surface of the component from which the coating has been removed and containing ends of said passages terminating at said first surface,
• b) directing a jet consisting essentially of a liquid at the second surface through the other end of at least one of said passages of step b) so the liquid penetrates the passages from the second surface to the first surface to remove at least a portion of the new coating located within or obstructing the passage to define a clear through passage between the second surface and first surface including through the new coating thereon;
• c) repeating step b) for all of the passages in the component until the passages have been substantially cleared of any coating located within or obstructing the passages.