Im not sure if the lines are original i want to say they are.
So here is the story again.I lost all pressure and braking wednesday and when I got home I checked the fluid and primary was almost empty so I filled it up.Then thursday morning I tried to drive it and had pressure for a second then lost it again but still have lots of fluid.But thats not to say there isnt a leak since I only tried driving it once since filling it up and for a very short distance.
That right there would be the sign of a leak somewhere and when it was so low air was able to make it into the lines. Not sure on the older body trucks but the new Chevy’s like to leak around the frame just under the Box sometimes they will get really bad on the back axle but that would depend on what type of weather area you live in NY is really tough so every truck I see at the shop has signs of rust and corrosion on the brake lines
I really hope that if its a 75 that they are not the original lines the lines on trucks now don’t last more then 5-6 years with out having a leak.
Auto Zone Advanced and everyone else sees brake line in rolls they now have the plastic coated lines that should hold up longer. Buy the rolls not the stright length and go from there if you find the spot that is leaking from I would say just replace them all front to back.[/quote]
If the truck was undercoated from the factory, the lines might be ok, when they start to go, the domino theory comes in. One pops, you fix it, pressure is greater and another one pops and so on.
I’d advise against using the rolled line unless you have great double-flaring skills. Most parts stores sell lines with the fittings installed in 10" increments up to 60". I use these a lot and are the best thing for driveway fixits.
If the line is a little too long, route the bends a with a bigger radius, avoid loops since they can trap air especially higher up in the system. If you have to do a loop, keep it horizontal. Longer sections can be joined with a union. Don’t let the lines chafe on anything that moves, they will rub through in time.