Brake Lines - Complete Set

Complete replacement of all brake lines from the master cylinder to all four wheels, including hard lines and flexible hoses on a 2007 Ram 3500 with 5.9L Cummins diesel 4WD.

Warnings

Tools required

Parts

• Complete brake line kit with pre-flared lines × 1 — Use OEM specification or quality aftermarket for 2007 Ram 3500 4WD
• Front brake hose (flexible line) - driver side × 1 — Use OEM specification
• Front brake hose (flexible line) - passenger side × 1 — Use OEM specification
• Rear brake hose (flexible line) - driver side × 1 — Use OEM specification
• Rear brake hose (flexible line) - passenger side × 1 — Use OEM specification
• Brake line mounting clips × 10 — As needed for replacement
• Rubber grommets for brake lines × 4 — As needed
• Copper brake line washers × 8 — Various sizes as needed

Fluids

• DOT 3 brake fluid — 2 qt

Preparation

1. Park vehicle on level, solid ground and set parking brake firmly
2. Place wheel chocks behind rear wheels
3. Photograph all brake line routing from multiple angles for reference during installation
4. Raise front of vehicle and support on jack stands positioned on frame rails
5. Remove all four wheels
6. Raise rear of vehicle and support on jack stands positioned on frame rails
7. Spray all brake line fittings with penetrating oil and allow to soak for 30+ minutes
8. Place catch pans under master cylinder and brake line routing areas
9. If replacing with custom-bent lines, lay out original lines to use as templates

Procedure

1. 1

   Remove master cylinder brake line connections
   Locate the master cylinder on the driver side firewall. Clean the area around all brake line fittings. Using appropriate size flare nut wrenches, carefully loosen the four brake line fittings at the master cylinder (two front circuits, two rear circuits). Work slowly to avoid rounding off the soft steel fittings. If fittings are seized, apply additional penetrating oil and use gentle heat if necessary. Allow brake fluid to drain into catch pan. Cap or plug the master cylinder ports immediately to prevent contamination.
   ⚠Use only flare nut wrenches, not open-end wrenches, to prevent rounding off the soft brass fittings.
2. 2

   Remove lines from ABS modulator and junction blocks
   Locate the ABS hydraulic control unit (HCU) mounted on the driver side frame rail below the master cylinder. Disconnect all brake lines from the ABS unit using flare nut wrenches. On 2007 Ram 3500, verify the exact number of lines at the ABS HCU before disconnecting, as inlet and outlet ports vary; carefully label each line to its port before removal. Trace lines to junction blocks near each axle and disconnect at those points. Remove mounting clips securing lines to the frame and body as you work. Keep track of which line goes to which wheel position.
   ℹ️Label each line with tape indicating its position (LF, RF, LR, RR) before complete removal to aid in installation.
3. 3

   Remove front brake flexible hoses
   At each front wheel, locate the flexible brake hose connecting the hard line to the caliper. Remove the bolt securing the hose bracket to the frame or knuckle. Using a flare nut wrench, disconnect the hard line from the flexible hose at the junction. Then remove the banjo bolt or threaded fitting connecting the flexible hose to the brake caliper. Discard old copper washers. Allow fluid to drain and immediately cap or plug all openings.
   ⚠Flexible hoses typically use banjo fittings with copper crush washers. Always replace these washers with new ones during reassembly.
4. 4

   Remove rear brake flexible hoses
   Trace the rear brake lines from the frame to each rear wheel. On this 4WD model, flexible hoses connect the frame-mounted hard lines to the axle-mounted hard lines or directly to wheel cylinders/calipers depending on brake type. Disconnect the flexible hoses at both ends using appropriate wrenches. Remove any mounting brackets or clips. On dual rear wheel models, note the routing carefully as clearance is critical.
   ℹ️Rear brake configuration varies by axle type (drum or disc). Verify your specific configuration before ordering parts.
5. 5

   Remove all hard brake lines from vehicle
   Working systematically from master cylinder to wheels, remove all hard brake lines from the vehicle. Remove all mounting clips and brackets securing lines to the frame, body, and axles. On this 4WD truck, lines run along both frame rails and cross over in several locations. Pay special attention to routing through frame holes and around suspension components. If fabricating custom lines, preserve the original lines as templates. Note the location of any protective grommets where lines pass through sheet metal.
   ⚠Some lines may be attached to fuel lines or other components with shared mounting clips. Do not disturb fuel system components unnecessarily.
6. 6

   Prepare and route new hard brake lines
   If using pre-bent lines, verify each line matches the original routing before installation. If fabricating custom lines, use the original lines as templates and carefully bend new lines using a tubing bender to match factory routing. Avoid sharp bends or kinks. Install new rubber grommets in all frame holes. Begin routing the main lines from the master cylinder location toward the rear, securing loosely with mounting clips. Ensure lines do not contact exhaust components, driveshafts, or suspension parts through full range of motion.
   ⚠️Brake lines must be routed away from all moving parts, exhaust components, and sharp edges. Contact with these items can cause line failure and total brake loss.
   ℹ️Do not fully tighten mounting clips until all connections are made and proper routing is verified.
7. 7

   Connect hard lines to master cylinder and ABS unit
   Start threading the brake line fittings into the master cylinder ports by hand to ensure proper alignment and prevent cross-threading. Once hand-tight, use flare nut wrenches to snug the fittings. Do not fully tighten yet. Similarly, connect the lines to the ABS hydraulic control unit, ensuring each line goes to the correct port as documented in your photos. Thread fittings by hand first, then snug with flare nut wrenches.
   ⚠Cross-threading brake line fittings will ruin the threads and compromise the seal. Always start by hand and verify proper thread engagement.
8. 8

   Install new front flexible brake hoses
   Install new flexible hoses at both front wheels. Use new copper crush washers on all banjo bolt connections. Connect the hard line end first using a flare nut wrench, then attach the caliper end with the banjo bolt and new washers. Secure the hose bracket to the frame or knuckle with the appropriate bolt. Ensure the hose has adequate slack and will not be stretched during full suspension travel or steering lock. Verify the hose does not contact the tire at full lock.
   ⚠Flexible hoses must have enough slack to accommodate suspension travel but not so much that they can contact moving parts or tires.
9. 9

   Install new rear flexible brake hoses
   Install new rear flexible brake hoses connecting the frame-mounted hard lines to the axle components. Use new copper washers where applicable. Ensure proper routing that allows for full axle articulation without stretching or kinking the hoses. On dual rear wheel models, verify adequate clearance to inner wheels. Secure all mounting brackets.
   ℹ️On solid axle vehicles, flexible hoses must accommodate significant axle movement. Test full suspension droop and compression before final tightening.
10. 10

    Final tightening and routing verification
    Working from the master cylinder rearward, systematically tighten all brake line fittings to proper torque specification. Since no torque specs are provided in the database, use general standards: consult the factory service manual for exact torque specifications. As general reference only, flare fittings are typically in the 10-18 ft-lbs range depending on line size and banjo bolts are typically 20-30 ft-lbs, but verify the specific values for this vehicle before final tightening. Secure all mounting clips firmly. Verify no lines contact moving parts, exhaust, or driveline components. Have an assistant cycle the suspension and steering while you observe for interference.
    ⚠Overtightening brake line fittings can crack the flare or damage threads. Tighten to specification plus 1/6 turn maximum.
    ⚠️Verify all lines are secure and properly routed. A line coming loose during operation will result in immediate brake failure.
11. 11

    Fill and bleed the brake system
    Fill the master cylinder reservoir with fresh DOT 3 brake fluid (verify DOT 3 vs DOT 4 in the owner's manual / on the reservoir cap) to the MAX line. Beginning with the wheel furthest from the master cylinder (typically right rear), attach bleeder hose to the bleeder valve and submerge the end in a container of clean brake fluid. Have an assistant pump the brake pedal several times and hold pressure, then open the bleeder valve to release fluid and air. Close valve before pedal reaches the floor. Repeat until fluid flows clear without air bubbles. Move to left rear, right front, then left front wheels. Keep master cylinder topped off throughout the process.
    ⚠️Never allow the master cylinder to run dry during bleeding. This will introduce air into the ABS unit, requiring specialized scan tool bleeding procedures.
    ⚠ABS-equipped vehicles may require a scan tool to cycle the ABS pump and valves for complete bleeding. If pedal remains soft after conventional bleeding, seek professional ABS bleeding.
12. 12

    Inspect all connections for leaks
    With the system bled, have an assistant firmly apply the brake pedal and hold pressure. Inspect every brake line connection, fitting, and junction for signs of leakage. Check the master cylinder, ABS unit, all hard line connections, flexible hose connections, and caliper/wheel cylinder connections. Tighten any weeping fittings slightly. If a fitting continues to leak, it must be disconnected, inspected for damage, and reconnected with proper technique. Wipe all connections clean and verify no seepage after 5 minutes of held pedal pressure.
    ⚠️Any brake fluid leak, no matter how small, is unacceptable and must be corrected before operating the vehicle.

Reassembly

1. Reinstall all four wheels and torque lug nuts to factory specification (typically 135 ft-lbs for Ram 3500, verify in owner's manual)
2. Lower vehicle to ground
3. Top off master cylinder reservoir to MAX line with DOT 3 brake fluid
4. Pump brake pedal 20-30 times to build pressure and seat all seals
5. Check pedal feel - it should be firm with no sponginess and should not sink slowly when held under pressure
6. Recheck all visible brake line connections for any signs of leakage

Verification

• Start engine and verify brake pedal does not sink with firm pressure applied
• Check that brake warning light is not illuminated on dashboard
• Perform a low-speed test in a safe, open area: At 5-10 mph, apply brakes firmly and verify vehicle stops straight without pulling to either side
• Perform progressively harder stops up to 25 mph in a safe area, verifying proper braking response and no pedal fade
• Inspect under vehicle after test drives for any signs of brake fluid leakage at any connection point
• Verify master cylinder fluid level has not dropped, indicating a leak
• Test brake performance with load by loading the truck bed with appropriate weight and verifying adequate stopping power
• Re-torque all brake line fittings and lug nuts after initial 50 miles of driving
• Monitor brake pedal feel and master cylinder fluid level for the first several hundred miles of operation

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