In life, there are high- and low-maintenance people. The high-maintenance ones usually need constant attention and reinforcement that they're performing well, while the low ones don't give you any trouble--until the day they go postal. The same can be said about many components in your truck. For example, there's the engine, which requires continual vigilance of oil and fuel. However, things don't get much more trouble-free than your vehicle's plumbing--until the day something bursts.
Whether you're in need of new hoses and accompanying components, want to swap in some hardware that will be more sturdy for your application, or simply yearn to dress up your ride, you need to have a basic understanding of what's out there and what will work where in your 4x4.
Your truck's plumbing is made up of hoses (or lines) that help route fluids from one area to another. Every vehicle uses hoses, and such conditions as pressure, rate, and temperature vary for each specific application. Carbureted vehicles typically come stock with hard line from the gas tank to the engine, with only a few pieces of rubber. The heater, water, and vacuum lines are almost always rubber, while the brake system has extruded soft steel hard lines, with the exception of flexible hoses near suspension components.
Rubber and hard lines are measured by their inside diameter (id); fuel lines are available in ¼, 5/16, and 3/8 inches; heater lines are available in 5/8 and ¾ inches; and vacuum lines in ¼ and 11/32 inches. Radiator hose is the only one not sized by id, but rather by application.
Since rubber has a shelf life, it can flake when you cut it and can't always hold up to the type of fluid running through it. People often switch to hard or braided stainless steel hose. Braided steel refers to its outside covering, while the actual hose comes in either Teflon-lined or standard neoprene rubber. The inside is essentially the same as high-quality rubber hose, but the braided-steel exterior makes the hose highly resistant to abrasion. It can also raise the burst pressure in some applications. The Teflon version is usually used for the brakes, while the neoprene is utilized for fuel and so on. A braided-steel covering can also be put over your existing rubber hoses if you want to dress up your plumbing, but these coverings are for appearance only. Braided line is used for the fuel, water, heater, and external oil lines (commonly seen in racing and performance vehicles), and it can even be found in the brake system because the Teflon lining has a stiffness and won't give like rubber can. However, when it comes to your brakes, you must buy the line premade and not make it at home.
Braided lines are sized by a dash number determined by their id in 1/16 inch. For example, a 3/8-inch fuel line would be -6. This is Army Navy (AN) spec, a standard that began prior to World War I to organize hardware, and is the industry standard. Fuel lines come in -4 to -12; water and heater lines in -10 and -12; and radiator lines in -16 and -20.
Now That's Fitting
A fitting (or connector) is the general category of hardware that connects hoses. Under that fall several different kinds of hose clamps and hose ends. First, let's talk clamps. A hose clamp is used to secure rubber or low-pressure braided steel over a fitting. For example, you attach rubber line to a carburetor by running the hose over the carb end and securing it with a hose clamp.
There are two main clamp styles: screw and spring. Screw-style clamps (or worm gear) simply wrap around the hose and then you tighten it. It's the standard ol' everyday stainless steel clamp. A spring type is a steel ring. You grab the end of the spring with pliers to open it, then slide it over the hose and it clamps automatically.
At the opposite end is the extended wing nut clamp, which is specialized and used in racing applications. It features a screw that's longer than a worm gear's, which allows you to tighten it by hand. There's also an Adel clamp, which is also called a nylon or cushion clamp. It has an aluminum band with a rubber insert that helps protect it from vibration. This clamp is used to secure lines along the framerails rather than to connect hoses.
We mentioned that a hose clamp can be used to secure a low-pressure braided line; however, the preferred way to make the connection is with a hose end for braided line and with an inverted flare for hard line. Hose ends come in straight, 30-, 45-, 60-, 90-, 120-, 150-, and 180- degree angles. It's comprised of a socket, a nipple, a cutter, and a swivel nut. Inside each swivel nut is a female AN thread (a male hose end is very rare) that connects the hose to a fluid source. Threads come in SAE, metric, AN, and pipe, and are male or female; male threads run on the outside of the adapter, female on the inside.
Now let's say you're connecting the transmission to the cooler and the threads on the hose end and the cooler are male and female. Well, that's a simple connection. However, if the hose end and the cooler both have female fittings, you need an adapter. An adapter converts the threads, and comes in straight, 45- and 90-degree configurations.
Often a factory hard line will run the length of the frame, then rubber line is used to connect to the fuel pump. The connection from hard to rubber can be made with a hose clamp because the flare at the end of the hard line will prevent the rubber from slipping off, and the clamp will seal it.
If the fuel pump has female pipe threads you need a pipe nipple fitting that's the same size as the rubber hose, which is usually 5/16 or 3/8 inch, in order to make the connection of the rubber line to the pump. Then you need an adapter with male pipe and a hex, which creates a barb similar to the flare at the end of a hard line. You'll need adapters for both the inlet and outlet sides of the pump. However, if you're connecting braided steel to the carb, you need an adapter with a hex for tightening.