Pro tip: I was wrong about using old brake fluid from a parts car
I swapped the master cylinder from a junkyard Civic into my project last month and thought the fluid looked fine, but after my pedal went soft on a test drive, my mechanic friend in Dayton said, 'Dude, brake fluid absorbs water from the air and that junk was probably five years old,' so now I always buy the new $8 bottle. Has anyone else had a cheap part almost ruin a bigger repair?