Replace a single damaged or corroded brake line section on a 2015-2020 Ford F-150 3.5L EcoBoost, including proper flaring, fitting installation, and complete system bleeding.

Warnings

Tools required

Parts

• Pre-fabricated brake line assembly OR brake line tubing (3/16" or 1/4" nickel-copper or steel) × 1 — Match OEM line diameter and length
• Brake line fittings (if fabricating custom line) × 2 — Match thread size of existing fittings
• Brake line mounting clips or brackets × 1 — As needed for routing

Fluids

• Motorcraft DOT 4 LV Brake Fluid — 1 qt

Preparation

1. Park vehicle on level surface, place transmission in Park, engage parking brake, and chock rear wheels
2. Locate the damaged brake line section and determine which wheel(s) will need to be removed for access
3. If replacing a pre-bent OEM line, obtain the correct part number for your specific model and brake configuration (front/rear, left/right)
4. If fabricating a custom line, measure the damaged section carefully including all bends and routing points
5. Raise vehicle with floor jack and support on jack stands at appropriate lift points per owner's manual
6. Remove wheel(s) as necessary to access the damaged brake line section
7. Clean the area around brake line fittings with wire brush and apply penetrating oil to fittings, allow 10-15 minutes to soak

Procedure

1. 1

   Prepare brake fluid reservoir
   Open hood and locate brake fluid reservoir on driver side firewall. Check fluid level and mark current level. Place clean shop towels around reservoir to catch any spillage. Do NOT remove reservoir cap yet, but have it ready for Step 2. Position a drain pan under the work area to catch brake fluid.
2. 2

   Disconnect damaged brake line at first fitting
   Using the appropriate size line wrench (flare nut wrench), carefully loosen the brake line fitting at one end of the damaged section. Hold the stationary component with a backup wrench to prevent twisting. Work slowly to avoid rounding the soft brass or steel fittings. Once loose, unthread the fitting completely and allow fluid to drain into pan. Cap or plug the open port immediately with a rubber cap or clean bolt to minimize fluid loss and prevent contamination.
   ⚠Use only line wrenches (flare nut wrenches) on brake fittings. Standard open-end wrenches will round off the soft fittings.
3. 3

   Disconnect damaged brake line at second fitting
   Repeat the disconnection process at the opposite end of the damaged line section. Remove any mounting clips or brackets securing the line to the frame or body. Carefully extract the damaged line, noting the exact routing path, bend locations, and any clearance points around suspension components, frame rails, or exhaust.
4. 4

   Fabricate or prepare replacement brake line
   If using pre-fabricated OEM line: Verify part number matches and compare routing to damaged line. If fabricating custom line: Cut new brake line tubing to length allowing 1/2 inch extra on each end. Deburr cut ends thoroughly inside and out. Create double flares on both ends using the flaring tool per manufacturer instructions - ensure flares are symmetrical with no cracks. Install brake line fittings with threads oriented correctly. Carefully bend line to match original routing using bending tool - avoid kinks, sharp bends, or flat spots that restrict flow.
   ⚠️Double flares MUST be properly formed without cracks, splits, or deformities. Defective flares will leak or fail under pressure. Practice on scrap tubing if inexperienced.
   ⚠Minimum bend radius is 10 times the tube diameter. Tighter bends will kink or collapse the line.
5. 5

   Route and install new brake line
   Route the new brake line along the exact path of the original, ensuring adequate clearance from all moving parts (suspension, steering, driveshaft), heat sources (exhaust), and sharp edges. Line must not contact any component that could wear through the tubing. Install mounting clips or brackets to secure line at factory locations. Line should be snug but not under tension or compressed.
   ⚠Verify brake line has minimum 1/2 inch clearance from exhaust components and will not contact suspension through full travel range.
6. 6

   Connect brake line fittings
   Start threading both fittings by hand to ensure proper thread engagement and prevent cross-threading. Once hand-tight, use line wrench to snug fittings. Tighten to finger-tight plus 1/4 to 1/2 turn - DO NOT OVERTIGHTEN as this will damage the flare seat. Use backup wrench on stationary component. Typical final torque is 10-12 ft-lbs for 3/16" line or 12-15 ft-lbs for 1/4" line, but feel is more important than exact torque - stop when fitting seats firmly without excessive force.
   ⚠Overtightening brake line fittings will damage the flare seat and cause leaks. Tighten until snug, not until wrench stops turning.
7. 7

   Fill brake fluid reservoir
   Remove brake fluid reservoir cap and fill to MAX line with fresh Motorcraft DOT 4 LV brake fluid. Keep reservoir at least half-full throughout bleeding process to prevent air from entering master cylinder. Monitor level constantly during bleeding.
8. 8

   Bleed brake system - furthest wheel first
   Begin bleeding at the wheel furthest from the master cylinder (typically right rear for RWD F-150). Attach clear hose to bleeder screw and submerge other end in catch bottle with small amount of clean brake fluid. Have assistant pump brake pedal 3-5 times and hold pressure. Open bleeder screw 1/2 to 3/4 turn while pedal is held down - fluid and air will flow into bottle. Close bleeder screw before pedal reaches floor. Repeat until fluid runs clear with no air bubbles. Check reservoir level frequently.
   ⚠️Never allow brake pedal to go to floor with bleeder open, and never let reservoir run dry during bleeding. Either will introduce air into ABS module requiring professional scan tool bleeding.
   Torque spec

   Bleeder Screw10 Nm (7 lb-ft)
9. 9

   Bleed remaining wheels in sequence
   Continue bleeding sequence: left rear, right front, left front (for standard RWD configuration). At each wheel, repeat the pump-and-hold bleeding procedure until fluid is clear and bubble-free. If the replaced line serves a specific wheel, pay extra attention to that circuit. Top off reservoir to MAX line after each wheel.
   Torque spec

   Bleeder Screw10 Nm (7 lb-ft)
10. 10

    Perform pedal feel test
    With engine off, pump brake pedal firmly 10-15 times. Pedal should become firm and hold steady pressure. If pedal feels spongy or sinks slowly, air remains in system - repeat bleeding process. Start engine (pedal will drop slightly due to brake booster) and verify firm pedal feel. If pedal goes to floor or feels excessively soft, DO NOT drive vehicle - repeat bleeding or seek professional service.
    ⚠️Spongy pedal or pedal that sinks to floor indicates air in system or leak. Vehicle is unsafe to drive until corrected.
11. 11

    Inspect for leaks
    With engine running and assistant applying firm brake pedal pressure (approximately 50 lbs force), carefully inspect all fittings on the new brake line for any signs of fluid seepage. Check both connection points and the flare seats. Wipe fittings dry and re-inspect after 30 seconds of sustained pedal pressure. Also check all bleeder screws are fully tightened and not leaking.
    ⚠️Any visible leak, no matter how small, must be corrected before vehicle is driven. Even minor leaks will worsen and can cause brake failure.
12. 12

    Reinstall wheels and perform final checks
    Reinstall wheel(s) and hand-tighten lug nuts in star pattern. Lower vehicle to ground and torque lug nuts to specification in star pattern. Top off brake fluid reservoir to MAX line and install cap. Clean any spilled brake fluid from painted surfaces immediately with water.
    Torque spec

    Wheel Lug Nuts140 Nm (103 lb-ft)

Reassembly

1. Verify all brake line mounting clips are installed and secure
2. Confirm brake line routing provides adequate clearance from all moving parts and heat sources
3. Double-check brake fluid reservoir is at MAX line with cap securely installed
4. Remove all tools, drain pans, and wheel chocks from vehicle
5. Dispose of old brake fluid according to local environmental regulations - do not pour down drain

Verification

• Start engine and verify firm brake pedal with no excessive travel - pedal should not sink when held under pressure for 30 seconds
• Perform low-speed brake test in safe area (empty parking lot): at 5-10 mph, apply brakes firmly and verify vehicle stops straight without pulling to either side
• Re-inspect all fittings for leaks after initial test drive
• Road test at gradually increasing speeds up to 25 mph in safe area, verifying normal brake operation and pedal feel
• After first 50 miles of driving, re-inspect brake line fittings, routing, and fluid level - address any issues immediately
• If ABS warning light illuminates, vehicle pulls during braking, or pedal feel changes, stop driving and have system professionally diagnosed immediately

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