How to Replace a Brake Line
Brake lines are the plumbing pipes and hoses that carry the brake fluid in a vehicle. Fluid from the master cylinder runs through the brake lines, under pressure, and activates the pistons in the calipers and wheel cylinders. The calipers and wheel cylinders have pistons that extend which push the friction material (brake pads or brake shoes) against the surface of the rotor or drum, which subsequently slows down the vehicle and stops it. If the steel line or rubber hoses that carry the brake fluid deteriorate, the hydraulic pressure built up in the system is lost. The brake pedal will drop to the floor, brake fluid will purge out of the breached brake line, and the vehicle will lose its stopping capacity. Steel brake line and rubber brake hose maintenance are critical.
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Things You'll Need
- Vehicle lift
- 1/2-inch drive impact gun
- 1/2-inch drive impact socket set
- Drain bucket
- Flare wrench set
- Box-end/open-end combination wrench set
- Penetrating lubricant spray
- Needle-nose pliers
- Ratchet and socket set
- Screwdriver
- Steel brake line (with proper flares and fittings)
- Brake hose replacement(s) with copper washers (supplied)
- Brake fluid (correct type specified for the vehicle)
- Safety glasses
- Latex gloves
Instructions
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How to Replace a Rubber Brake Line Hose
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1
Open the hood and check the brake fluid level in the master cylinder. Top it off with brake fluid and replace the cap/cover. If a hood light is present, disconnect the light or close the hood so the light does not drain the battery during the repair.
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2
Lift the vehicle to a comfortable height to remove the wheel(s). Use a car lift that suspends the vehicle's wheels (not a drive-on ramp lift).
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3
Wearing safety glasses and latex gloves, remove the hubcaps and then loosen and remove the lug nuts using an impact gun with an impact socket. Take off the wheel.
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4
Place the drain bucket on the floor beneath the rubber brake hose.
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5
Locate the bleeder screw on the hydraulic component (caliper or wheel cylinder) and loosen it with a box-end wrench to make sure you can break it open when the bleeding-brakes procedure is needed. It is recommended that you make sure the bleeder screws of all the wheels can be opened for proper bleeding. If not, the hydraulic components (calipers/wheel cylinders) may need to be replaced. Retighten the bleeder screw.
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6
Spray penetrating lubricant on both sides of the rubber hose connection and on any bolt or screw clips retaining the brake hose. Allow 10 minutes or so for the penetrating fluid to soak in.
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7
Remove any retaining clips or brackets with a ratchet and socket or box-end wrench that are securing the brake hose to other components like the strut, for example. Use the needle-nose pliers to remove the metal clip securing the brake hose to the brake line connection.
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8
Disconnect the rubber hose from the caliper (on disc brakes) using a ratchet and socket to remove the retaining bolt from the caliper, or the hose to the steel brake line (for rear drum brakes). Use a flare wrench to loosen any steel brake line connection so you do not round out the fitting of the brake line. Wiggle the flare wrench and move it back and forth slowly while holding the hose fitting with an open-end wrench to successfully separate the steel brake line fitting from the brake hose. The fittings on the steel brake lines need to be able to be moved freely without holding the steel brake line. After time, the fittings may corrode to the brake line and trying to remove them without care will result in collapsing the steel brake line or breaking it. If a steel brake line fitting will not separate freely, replacing the steel brake line.
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9
Remove the copper washers from the brake hose retaining bolt (banjo bolt) and caliper housing (disc brakes). Picking them out with a screwdriver may be necessary.
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10
Install the new rubber hose by reversing the procedure. Be sure to replace the copper washers correctly and tighten properly. Replace the retaining clips and brackets.
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11
Lower the vehicle to check the brake fluid level and then top it off again if necessary. Bleed the brake system and then check and adjust the fluid level in the master cylinder again. Never allow the master cylinder reservoir to run dry. If the bleeding process is taking longer than expected, check the master cylinder and then add fluid as necessary during the bleeding procedure.
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12
Replace the wheel, lug nuts, and hubcap. Test-drive the vehicle.
How to Replace a Steel Brake Line
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13
Open the hood and check the brake fluid level in the master cylinder. Top it off with brake fluid and replace the cap/cover. If a hood light is present, disconnect the light or close the hood so the light does not drain the battery during the repair.
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14
Wearing safety glasses and latex gloves, lift the vehicle high enough on a car lift to access the compromised steel brake line.
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15
Place a drain bucket beneath the brake line. Spray penetrating lubricant on the connections of the steel brake line and allow at least 10 minutes for it to soak in.
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16
Follow the brake line to each of its connections. A body line may run from the master cylinder all the way back to a rear wheel. This could require removing the brake line from the master cylinder (and capping it off so the reservoir does not drain dry) and then re-lifting the vehicle to remove the rear connection. Rear brake lines are shorter and easier to access.
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17
Disconnect both connections of the brake line (one at a time) using a flare wrench on the brake line fitting and an open-end wrench (or another flare wrench) on the union connection (some brake lines may run into ABS units or proportioning valves). Wiggle the flare wrench to loosen the free-floating fitting on the brake line while holding the union or other connection (if applicable) with another wrench to stabilize it.
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18
Install the new steel brake line and tighten the fittings.
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19
Lower the vehicle to check the brake fluid level and then top it off again if necessary. Bleed the brake system and then check and adjust the fluid level in the master cylinder one more time. Never allow the master cylinder reservoir to run dry. If the bleeding process is taking longer than expected, check the master cylinder and then add fluid as necessary during the bleeding procedure.
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20
Test-drive the vehicle and recheck for seeping brake fluid afterward.
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Tips & Warnings
Steel brake lines have specific fittings and flares designed differently on most vehicles. You will have to match the fittings and flares correctly to replace the steel brake line. It is not always suitable to purchase new steel brake line before removing the old because you cannot assume the vehicle (no matter what make or model) was manufactured with a specific brake line fitting. You will most likely need to remove the steel brake line and then bring that to the parts store to match up the lengths and fittings and unions. Steel brake line also comes in certain lengths so if you're replacing a body line, you may have to use two lengths of steel brake line with a union fitting in between to achieve the correct length. You can also purchase spooled steel line and cut your own lengths with a pipe/tube cutter and make your own flares with a flaring kit and add your own fittings (to accommodate the connections). Always refer to a repair manual for possible bleeding sequences for the specific vehicle to ensure there are no air pockets remaining in the hydraulic system.
