Brake Line Replacement

I'm finally at the point of getting my wagon back on the road, can anyone verify the size of the rear brake line? I measured, albeit very crudely 5/16" for the line along the frame and the lines on the axle at 3/16". Looking at getting ~4' pieces for the axle to bend it properly, the section on the frame is also approximately 4' to the section that was previously replaced.

Further research points to the main line being 1/4" I really need to get some measuring calipers. Now my big debate is to get sticks of line with the fittings already attached or to get bulk line and rent a flaring tool and bender. I'll probably go for a bender since there's 2 90* bends of different radii.

The lines have bubble flares at all ends. A bubble flare is, for the most part, an unfinished double flare. If you are going to replace part of the line, you will find that the OEM lines are extremely hard to flare, no matter what type of flare you choose to do. The lines are metric, and will not flare correctly with an SAE flaring tool. The SAE lines will not flare correctly with a metric flaring tool as well. I forget what the diameter of the rear line is. Most of the parts stores have SAE lines with metric fittings that will work with the B-body fittings. Do not make a single flare, it will not seal properly. If you choose to make an unfinished double flare as a bubble flare, you will probably have to tighten the fitting to a great degree to compress the bubble enough to seal. That is why I chose a double flare for the fittings that I added to the lines on my car. You still have to tighten them a lot to get them to seal.

If you have not used a flaring tool before, or have had poor results, there is a technique for using it properly...Put your tubing in the proper place, and tighten the thumb screw on the end CLOSEST to the tube, then tighten the far end. It gives the highest clamping force on the tube, so that it does not slip when making the flare. Remember to put the nut on the tube before flaring the end.

I removed the ABS from my car, and used double flares for the fittings I used on the ends of the OEM line stubs. The lines from O'Rileys were easiest to flare. I purchased one with a bubble flare, and cut one end to double flare it. I double flared the stub end of the OEM line, and used a coupler for metric fittings. If you go to the parts store, they will allow you to compare the line sizes to get the correct one.  You can NOT use a bubble flare nut on a double flare end, and vice versa.

You can detach the single line from the ABS unit, and cap the unit to keep the fluid from draining while working on the line. I allowed the farthest fitting to be loose as I reassembled the line to the system, and allowed the brake fluid to fill the line. It kept bleeding to a minimum. If you keep the cap on the master cylinder, the vacuum will minimize fluid loss as you work. Keep an eye on the fluid level in the master cylinder, it must be removed to bleed it if you run it dry.

If you have trouble getting the fitting nuts off, as a last resort, there is a tool called a butterfly socket. I have never had one damage a fitting nut, no matter how tight it was. I have even removed one where I had to stand on a wrench holding the part, and use my foot to push an 18 inch breaker bar (with the butterfly socket) on the fitting. It did not damage the fitting nut. They are expensive, but will become one of your favorite tools.

Most of the line going to the rear has already been replaced, it has a standard double flare on the end. I have never flared lines myself, I was actually considering getting sticks of pre flared line, just as long as the fittings will go into the wheel cylinders and the brake hose to the axle. The old line was leaking around the 90* bend, by the air ride compressor below the left rear door. I'm replacing the axle lines with single pieces to the hose, they've been repaired before.

My grandfather's line wrenches have been working great.

Do the wheel cylinders really take a bubble flare? I've considered getting line without flares and renting a flaring tool.

I have not replaced rear brake cylinders for a few years, and do not remember whether they had bubble flares or not. I am assuming that they are bubble flares because everything else is bubble flares. You can check one at the local parts store to determine which type of flare it takes. If it has a smooth bottom of the hole, it is for a bubble fitting. The bottom of the hole will have a reverse flare for the double flare.

You can only get line in 25 ft. rolls, and if you are replacing two sizes, you need two rolls. The sections with finished ends come in sizes up to 50 inches. There may be a stock length that can be bent to fit the axle. Remember that the fittings are metric, even if the line size is SAE.

I found it difficult to remove the hose going to the flex line from the body. The space is limited, and difficult to get a wrench in the space.

Here's what I have found out, the wheel cylinders take a normal double flare, just like is on the axle end of the hose. I asked to look at a wheel cylinder and brought my new hose with me at the parts store.
I have 2 sticks of 3/16"x51" line to redo the axle lines completely. The other end of the hose takes a bubble end, the front hoses also have a bubble end as well. The parts store did not have a double flare to bubble adapter or anything else to make it work. Fortunately, I work at a Buick-GMC-Cadillac dealership right now, I should be able to talk to the service guys tomorrow and see what they have. I should have thought about this route before, as an employee its 10% over cost for parts.

It appears that you have our issues solved. The guys at the dealership should be able to fix you up. There may even be a set of lines still in production for a truck that will fit your car.