The use of carburetor heat is too late if the engine has become cooled to the point where it is unable to melt any existing ice.
(The use of carburetor heat; is; too late) (the engine; has become cooled; ) (it; is; unable to melt any existing ice; L:the point) (it; to melt; any existing ice)
The use of carburetor heat the engine it it
is has become cooled is to melt
too late
unable to melt any existing ice L:the point
any existing ice