A common upgrade performed on a car’s braking system is the car’s brake lines. The car’s existing rubber brake lines are replaced for a stainless steel-braided brake line. This is done to improve the “feel“ of the brake pedal. Since the steel-braided line is more resistant to expansion than the rubber line, a more firm pedal pressure is experienced. This instructable will cover the replacement of the brake lines on a 2000 Mazda Miata at the Menlo Park Techshop, using the autobay (I made it at Techshop, http://techshop.ws).
Step 1: Gather Your Tools
- Floor Jack
- 4x Jack Stands
- 21mm deep socket
- 10mm flare nut wrench
- 12mm, 10mm socket
- 8mm box wrench
- ¼” clear tubing
- Torque wrench
- Empty bottle
- Pliers or a vice grip
- A friend to help bleed the brakes
- Turkey baster
- Steel Braided brake line kit
- Brake fluid
Step 2: Raise the Car Onto Jackstands
I used the crossmember in the front of the car as a jacking point for the front wheels. Since the front wheels spin freely without somebody pressing on the brake pedal, it is a good idea to loosen the lugnuts with some weight on the wheels prior to completely lifting the car up with the jack.
I used the rear differential as a jacking point for the rear of the car. If the differential is too low for you to fit a jack underneath, try jacking just one side of the rear wheels up and slipping a 2x4 or two underneath. Then try the differential again. I placed the jackstands at the pinch welds at each corner of the car.
Step 3: Remove the Wheels
The Miata has 21mm lug nuts. Depending on your wheels, you may or may not need a deep socket to remove them. With stock wheels, I typically use a cross-wrench on the wheels.
Step 4: Remove the Banjo Bolt
Use your 12mm socket to remove the banjo bolt connecting the flexible brake line and the brake caliper. There should be 2 washers at each banjo bolt. Remove both of these as the new brake lines should come with new ones.
Step 5: Disconnect the Flexible Line From the Hard Line
Use your 10mm flare nut wrench to loosen the flare nut at the connection between the hard line and the flexible brake line. Be careful not to round the nuts. They are relatively soft and it is easy to strip the corners off. This will make tightening them very difficult.
Step 6: Remove the Brake Line Bracket
There is a bracket holding the flexible line in place. Use pliers or a vice-grip to remove this piece.
Step 7: Install the New Brake Lines
Installation of the new brake lines is the opposite order of the removal.
This process applies to the front brakes as well as the rear driver-side brake.
Step 8: Passenger-side, Rear Brake
On the rear passenger-side, there is a distribution block that the flexible line and two hard lines connect to.
Loosen the two flare nuts connecting the hardlines to the distribution block. Use a 10mm socket on the two nuts mounting the block to the chasis. Then remove the banjo bolt on the caliper similar to the other brakes. Installation is going to be the reverse of this.
Step 9: Empty the Brake Master Cylinder Reservoir
Use the turkey baster to empty the brake master cylinder reservoir of the old brake fluid. Then refill the reservoir with new fluid.
Step 10: Bleed the Brakes
Since the brake lines were removed, air was introduced into the braking system. This air will need to be removed. Start at the passenger-side rear brake.
- Slip your 8mm box wrench over the brake caliper bleeding valve and then place your plastic tubing over this. The other end of the tube should be in the empty bottle you have for collecting brake fluid.
- While you sit at the brake caliper, have your friend sitting in the driver seat.
- Have them press on and hold the brake pedal.
- Then you loosen the bleeder valve by about a quarter-turn. Brake fluid with bubbles should be making its way through the connected tubing.
- When the fluid/air is no longer coming out, re-tighten the bleeder valve.
- Have your friend release the brake pedal and re-apply and hold pressure again.
- Then you loosen the bleeder valve again.
- Repeat this process until no air is coming out of the caliper with the fluid.
- Occasionally check on the fluid level in the reservoir.
- Top this off with new brake fluid as necessary.
- When finished, move on to the rear driver side, the front passenger side and finally the front driver side.
Step 11: Remount Your Wheels
Be sure to tighten your lug nuts to the appropriate torque and in a cross pattern. Generally, 85 ft-lbs is a good number to tighten to if you don’t have a service manual handy. Then lower your car back onto the ground. Be sure to test your brakes before driving around. The brake pedal should be firm and should be effective early in the pedal travel. If this isn’t the case, you may still have air in your brake lines and you will need to re-bleed them.