[dsraven]

make sure to reroute (thats what i would do) or insulate the brake lines well. brake fluid likes water and will absorb condensation. then the moisture rusts the internals out prematurely. hot/cold allows condensation, too hot allows the fluid to boil, usually poor brakes at that point.
if the fluid is getting too hot and discoloration occurs you should bleed them till you get fresh fluid at all the wheels, then make sure to fix the heat problem.
i am with whoever said "go for a ride (on a back road away from traffic) and wait till you have some tight wheels, then crack a bleeder and see if the fluid is under pressure". if it is then chuck those valves. another thing to check is if the pedal is bouncing while you drive and effectively "pumping up" the system. could be a weak return spring allowing that? seems like a lot of linkage with the underfloor systems.