Yesterday I dove into the wonky master cylinder. The back boot was loaded with brake fluid. You could say I found the smoking gun. On the bright side, it is the original unit to the car. GM sourced the master's from Bendix originally. This one being dated the 342 day (Bendix did not cast the year into the casting) which equates to December 8th of 1965. Right in line for a January built car.
I found a decent amount of corrosion on the bottom of the cylinder back by the rear seal. I honed the hell out of it, but it will need to be sleeved. I have new master on the way, so I can get the car back on the road. I'm honestly impressed the car made it this far with it's original master. At some point, I'll get it reinstalled. Spring is in the air here in the northwoods of Wisconsin
