Originally Posted by rodzghost
Thanks for the in-depth reply.
Like rubbertoe mentioned depending on the brand of fluid... if it was really that low quality + humid environment (not sure where you live) it has the potential to turn bad quickly. Just be sure to buy a quality brand name DOT4 fluid when you do it again (stay from store/generic brands)
Taking the lines off isnt totally necessary but is the best way to completely empty the system. The problem with this way is bleeding can take longer. When people empty the reservoir, refill with clean and open the bleeder till it runs clean is the quick and easy way when your system is relatively clean to begin with. Because you don't know the level of contamination I would pull everything and start clean and fresh.
May not need a gasket but if its easily accessible and cheap its peace of mind. If you're taking the line off you're going to need crush washers(debatable on there reusability) or just buy an SS line and the gasket.
If it were me....
Id start with sucking out the reservoir, then catch what comes out the bottom of the brake line in a different container and see what it looks like coming out. If its nasty you could be in for more work down the road... if its clear/yellow/brown/dark brown should be okay
In addition to those guides I posted, when you take the caliper off, with the line removed, clean your pistons and squeeze them back with it off the bike and check the fluid color that comes out. *NOTE* I havent done this myself so I have no idea if the pistons have back stops or not. When the caliper is disconnected they will push back fairly easy, dont ram them back, and try not to bottom them out, just so they sit flush on the front where the pad would sit.
Either put on a new brake line or waste some new brake fluid and rinse the line, fill it with a little bit of new fluid, hold it in the air and do the see-saw, swash it around and drain it out, hopefully this will take any potential left over moisture out with it.
Rinse out your res with a bit of brake fluid and wipe clean with a lint free
Re-assemble with new sealing hardware, refill, spend what will feel like a life time bleeding it and you're good to go.
Id pop the res cap off every 4 or 5 weeks and see if its turning color quickly... if not you should be good for another couple years depending on fluid quality and environment yada yada yada
If its browning/blackening quickly, well if your not leaking it anywhere... could just be a bad casting on your reservoir or something.... thats when you start diagnosing further and throwing more money at it haha