There is no "overflow" function in the monovalve. If the housing is cracked and you cannot seal it up with glue or whatever, you must replace the entire monovalve. The casing is not and never was available as a separate part. If you are on a budget, try to find a used one at a junkyard or from someone on this forum.

__________________

"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .343,000 miles Wife's car
2005 E320 CDI . . 148,000 miles My car
Santa Rosa population 177,300 (2026 projected)
Total. . . . . . . . . . . . 668,300
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970