Project Mustang Part 3: How To (Safely!) Restore Brake Hydraulics

What to do when your brakes hit the wall and your wallet needs a break!

Safety is of the utmost importance for any vehicle, but even more so when it is your kid’s first “cool car.” Up until now, we have been focusing on making the Project Father-and-Son 1969 Mustang capable of moving under its own power, upgrading the steering to rack-and-pinion, and repairing the Fred Flinstone floors, now we need to make it stop. The brakes are non-existent, and we need to find out why.

We bought this car as an unfinished restoration project; the previous owners did things they were capable of, then found themselves neck-deep in rusty floors, so they sold it. The front discs and rear drums had been serviced with new calipers, rotors, pads/shoes, and hardware. What had not been serviced were the brake lines and master cylinder. The liquid inside the master may have been brake fluid at one point, but it certainly is no longer. We ordered a new Duralast master cylinder and rubber brake lines from our local Autozone and got to work.

Swapping the master is two bolts and two lines plus a little bench-bleed, which is easy. But down the line there will be more serious issues, namely cracked hoses and missing hard lines. When we inspected the rubber lines, we found that they looked good at a glance, but a closer inspection showed that the ends were cracked and split. They might be OK for a little while but why take the risk when they only cost a few bucks to replace?

Before putting a wrench on the lines, we sprayed them with some Justice Brothers JB80 penetrant to help break the threads loose. Virtually all 3/16-inch hard line nuts get rounded off when they are relatively new, so it is even worse when they are 50 years old. We used a line wrench, which captures four of the five sides of the hex to keep the nut from rounding off, but the JB80 makes the job so much easier. We were lucky to escape with both front lines unthreading clean. If you do round off the nut, it has to be cut off and re-flared with a new nut, which shortens your hard line by at least 1/8 inch. Sometimes you have enough length to get away with it, and sometimes you have to replace the entire line or put in a splice. Either way, it is no fun fixing it. The new rubber lines bolted to the subframe and calipers just like the originals. Do not forget to install new copper washers under the head of the banjo bolt and the banjo fitting to the caliper, otherwise you will have a massive leak.

Out back we had a bit more trouble. The original rubber hose was gone, along with the rear axle vent, which is also the bolt that holds the distribution block to the axle tube. We had to order one online, so we used a 7/16-14 bolt with a jamb nut to hold the new rubber line in place until the new vent arrives. We had to do this because the hard lines were not on the rear axle either. We could order some pre-bent lines, but that takes time and frankly, we have the ability to make them in-house.

You need the following to make bent hard lines: double-flaring tool, hard line, fittings, tubing cutter, tubing bender, and some baling wire or a coat hanger. Using the distribution block on the rubber line and each wheel cylinder on the backing plates as the anchor points, we bent up some baling wire into the right shape and length to match up to the two anchor points for each side. You need to add about a 1/4 inch to each side for flaring, and exaggerate the bends a little so you have some extra line for the future, should you need to cut and flare the line again down the road. The axle housing has a couple of bent tabs welded in place to lock the line to the housing; make sure you use these in your new brake line layout.

The baling wire serves as the pattern for the new line, which we have in a coil. We buy this stuff online and it’s usually $25 for a 25-foot roll and a pack of fittings. If you don’t have the line on hand, you can always pop down to your local parts store and buy a stick of Poly Armor brake line, which has the fittings and both ends are flared. (You will need to cut and re-flare one end.) Poly Armor brake line is really nice because the alloy they use is soft enough to bend by hand without a tool. A tool makes it look better, but you can get away with hand-bent lines if you need to. If you use the rolls like we do, you need a line straightener; we picked up ours online for about $140.

With your straight line, start on one end, making sure the fitting is against the flare (this is very important, once bent, the fitting can’t move) and mark out your bends. Using the bending tool (you can even borrow one from AutoZone), carefully bend each section to match the bend and the orientation of the bend. Check each bend against the pattern to make sure you have it right. You can straighten a section if necessary, but only if you catch it before you get to 45 degrees; anything more and you will likely just kink the line. If you do need to un-bend a section, use a bench vise and work slowly to prevent kinks.

Once you have the bends made, you need to check the fit to the car. If you don’t have it just right, now is the time to adjust it. Leave the last end long so you can trim it up just right. With that set, trim off the excess, slide on the fitting, and get out the flaring tool. We are using a hand-operated flaring tool from Eastwood. This thing is awesome, it uses special dies and has a rotating head to make perfect double flares every time in about 30 seconds. It can’t be used on the car though as it is a bench vise–mounted unit. They have heads for 45-degree double flares (standard flare), as well as one for 37-degree single flares for AN-style fittings. This rig is so much easier than using a clamp-and-die style flaring tool. If you are using the clamp and die kit, make sure that the tubing matches the ridge on the die when you lock it into the clamp, otherwise your flare will leak.

We spent about four hours replacing and building new lines for the Mustang, and now everything looks great and holds the pressure for safe braking. We were planning on replacing the wheel cylinders, but everything looked new inside the drum so we are going to try them out and see. The expensive flaring and straightening tools are not required for this job, you can always borrow a flaring tool from the parts store with a small deposit, but if you are going to make a bunch of lines, they are worth every penny. Don’t forget to the bleed the brakes when finished!

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