Green’s Dictionary of Slang

klunk out v.

[var. on conk (out) v.]
(US)

1. to break down.

[US] in S. Terkel Amer. Dreams (1980) 162: The machine klunks out, an’ it’s us that are fixin’ it.

2. to faint or fall down.

‘wyrydernona’ Epinions.com 23 Dec. 🌐 Kelly hears the news, klunks out on the floor.