Master Brake Cylinder / fluid

[Izzy]

so i noticed the brake cap was not on properly after we bled the brakes and purged all the air out of the system. the car wasn't turned on again after allof this and i saw this while i was doin other work. Got a new cap, turned her on and the brakes seem fine .. however i remember readin that its possible the brake fluid absorbed moisture from this cap not being on properly. What do you all think? i've only added fluid to do the bleeding . i've never fully a purged all the fluid and put in all new fluid .. so if thats the case ... can anyone give me a short walk thru or tips? thank you

1991 pontiac trans am v8 305 TPI automatic

[BANSHEE001]

Its good to change the fluid anyway. Temps going up and down cause moisture in the lines. All I do is losen all wheel bleeders. Let the old brake fliud come out while you put new fluid in the master. make sure the master never runs out. watch the bleeders for the fluid clearing up. when the fluid looks clear the old is out.

[TraceZ]

I changed my fluid last fall. I used a vacuum pump to do it. First I sucked all the fluid out of the reservior and replaced it with fresh fluid, then I bled it at the ABS unit until it was clear and then the rear bleeders, then the front bleeders. You just have to make sure you keep the reservior full.

[Izzy]

thank guys