when do i know to change this or when its not workin properlly?

i felt today that i had to press extra hard to get my brakes working and found out that the fluids was low. i topped that off but it still doesnt feel 100%

changed out front brake pads and rotar not to long check rears and there fine.

anything else it could be?

thanks

 

Was the fluid black in the reservoir, because over time, brake fluid eats away are the rubber o-rings that keep everything sealed, and they start to leak.

 

One of the few things i learnt in auto class was, somtimes you get a clots in your lines and they have to be bled out

 

bleed out the line today brakes back to normal

and no it wasnt black but was really low? hm..