One thing that could be an issues is if you have a faulty seal inside of the Hydrovac. There should be a plug on the back of the power piston cannister where a very small amount of fluid is added to lubricate the power piston. If you pull that plug and brake fluid comes out, youll know what the problem is and why its fine for a little while and then gets squishy as time rolls on since its slowly leaking past a seal every time the brakes are pushed.
Theres a long list of vendors under the links section at the top of the page. A few good ones being Jim Carters, The Filling Station, Chevs of the 40s, etc.
Good luck! Jeff
