Most of us know that we need to go through the hydraulic cylinders and mechanical parts of our classic’s brake system periodically, but not as many seem to understand how important it is to replace the system’s hydraulic tubing
Rust and dents on the outside of brake tubing can weaken it and make it unsafe, but worse than that, the conventional DOT 3 (DOT stands for the Department Of Transportation in the United States) brake fluid most systems have in them attracts moisture that rusts out steel brake tubing from the inside, and decreases its bursting point even further.
Replacing the brake tubing should be part of any restoration. It’s easy to do, and can go a long way toward making your classic safer to drive. Replacement is also necessary for cosmetic reasons if you plan to show the vehicle.
All you need to do the job is a tubing cutter, a tubing bender, a flaring tool, the correct brake nipples, and the tubing itself. Tubing is sold in various lengths, but it is generally best to buy it in 10-metre coils rather than trying to piece together individual tubes.
Brake hydraulic lines should always be made of steel. Copper tubing won’t do because it does not have a high enough bursting point. Brake tubing must also be double-flared at the ends for extra strength. A single flare tube can fatigue and leak. Bending steel tubing is easy if you have a bending tool to avoid kinking, and for gradual bends you can even do it with your bare hands. Flaring requires a special tool available from automotive tool stores.
Starting work
Remove each tube from the chassis one at a time, then use the old tube as a template for bending the new one so you won’t get confused. Cut the tubing about three centimetres too long to avoid problems when flaring. Save any clips for holding the tubing in place, as well as any brass tees or other fittings such as are usually found on the rear axle housing and at the front of the chassis where the brake tubing splits off.
Cut the tubing to length, then file its ends flat and bevel their edges. Bend the tubing slowly and gently, using a tubing bender so as not to kink it. When you have it the way you want it, try the tube in its location to make sure it fits properly before adding nipples. After any minor adjustments, you are ready to flare the ends. Pop a nipple on the end of the tube and push it down out of the way.
Now place the tube in the holder part of the flaring tool and make sure it sticks up at the right height by using the forming tool as a guide. Compress the forming tool over the end of the tube, then remove the forming tool and use the compression tool to finish the double flare.
Brake Bleeding: An essential part of any operation on your car’s braking system
| The bleeder nipple (on the back-plate of drum brakes or, as here, on the calliper for disc brakes) should be free of dirt and grease before attaching the plastic tube |  |
| The free end of the tube should be completely immersed in a jar containing hydraulic fluid throughout the bleeding process. If air is drawn back into the system you’ll have to start all over again |
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| After bleeding each brake, top up the reservoir with fresh fluid (see your car handbook for correct type). Do not contaminate the fluid with dirt, oil or water |
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| When bleeding or checking master cylinder reservoir, always ensure cap is clean before removal or replacement. Also, make sure air hole in cap is clear before replacement |  |
Changing Hydraulic Brake Lines
| Tools required to replace brake hydraulic lines are: pipe cutter, tubing bender, flaring tool. You will also want to buy a 10-metre roll of steel tubing, and the required nipples for your make |  |
| Cut the tube to length using a pipe cutter. Tighten the tool, turn one full turn, tighten again and turn again. Repeat until the tube is cut |  |
| Clean the end of the tube using the de-burring tool on the tubing cutter |  |
| File the end flat, then bevel the tubing for flaring |  |
| Measure the height of the flare using the bottom of the forming tool in the flaring tool kit as a guide, then clamp the tubing in the holder |  |
| Forming tool is tightened into place. |  |
| This step creates a rounded bell |  |
| Clamp and flaring tool are used to make the final, double flare |  |
| Brake line wrench helps prevent rounding nipple flats |  |
| Front tubing usually goes behind front cross-member and over to passenger side front wheel |  |
| While you are replacing your brake system’s hydraulic lines, replace the three flex hoses as well for safety reasons |  |
Words & Photos: Jim Richardson
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