John - There's one other possibility that may be involved. The below screenshot is from a 1947 Chevy Truck Shop Manual, which is still applicable in your case as the Huck brake system remains the same. There is a possibility that your master cylinder has an obstruction in the compensating port which is preventing fluid return to the main cylinder. headscratch

PS - This page covers checking the clearance for the compensating port in the MC.
Attachments

Last edited by Gdads51; 06/20/2026 1:24 AM. Reason: add PS
~ Dan
1951 Chevy 3 window 3100
Follow this story in the DITY Gallery
"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)