Have you replaced the rubber brake hose at both front wheels (should do the rear as well)? They can look fine, but be swollen on the inside and act like a check valve.
Mike B
Mike Boteler
1956 Chevy 3100 Resto Rod 1952 Willys M38 Army Jeep 1983 Jeep CJ7 Laredo 1984 Jeep CJ7 +++++ Silver Spring, MD