Brake Line - Single

Replace a damaged or corroded brake line section on a 2007 Ram 3500 with 5.9L Cummins diesel engine, restoring safe brake system operation.

Warnings

Tools required

Parts

• Brake line section (3/16" or 1/4" steel brake tubing, match original) × 1 — Use OEM specification or equivalent nickel-copper brake line
• Brake line fittings (if not using pre-flared line) × 2 — Match thread size to original fittings
• Brake line mounting clips × 2 — As needed for routing

Fluids

• DOT 3 brake fluid — 1 qt

Preparation

1. Park vehicle on level, solid surface and apply parking brake
2. Place wheel chocks on all wheels not being lifted
3. Locate the damaged brake line section and identify which wheel circuit it serves
4. Determine if wheels need removal for access (typically required for lines near wheel wells)
5. If working near wheels, loosen lug nuts before lifting vehicle
6. Raise and support vehicle on jack stands at appropriate lift points for the frame
7. Remove wheels if necessary for access to brake line
8. Clean area around damaged brake line and fittings with wire brush and penetrating oil
9. Have replacement line ready - measure damaged section to determine required length if fabricating custom line
10. Verify replacement line matches original diameter (typically 3/16" for most circuits, 1/4" for some rear lines)

Procedure

1. 1

   Prepare brake fluid reservoir
   Open hood and locate brake fluid reservoir on driver side firewall. Remove reservoir cap and use a turkey baster or fluid extractor to remove brake fluid until level is at minimum line. This prevents overflow when disconnecting lines. Dispose of old fluid properly - do not reuse.
2. 2

   Mark and photograph line routing
   Before removal, take photos of the brake line routing, mounting clip positions, and relationship to other components. Mark the line orientation at both connection points with a paint marker or tape. This ensures correct routing during reinstallation and prevents line kinking or contact with moving parts.
3. 3

   Disconnect brake line at first fitting
   Using the appropriate size flare nut wrench (NOT a standard open-end wrench), carefully loosen the first brake line fitting. Verify the flare nut size before loosening; brake line fittings on this platform are commonly in the 10mm to 12mm (or SAE 3/8") range, but confirm with the actual fitting. Hold the component (caliper, wheel cylinder, ABS module, or junction block) steady with a backup wrench to prevent twisting. If fitting is seized, apply more penetrating oil and allow to soak. Do not force - rounded fittings require complete line replacement to next junction point.
4. 4

   Disconnect brake line at second fitting
   Move to the other end of the damaged section and repeat the disconnection process. Once both ends are free, brake fluid will drain from the line. Position catch container to collect fluid. Cap or plug open brake line ends and component ports immediately with rubber caps or clean rags to prevent contamination and further fluid loss.
5. 5

   Remove mounting clips and extract old line
   Release all mounting clips securing the brake line to the frame, body, or suspension components. On 2007 Ram 3500, these are typically plastic push-clips or metal spring clips. Note the exact position of each clip for reinstallation. Carefully remove the old brake line, noting how it routes around obstacles and other components.
6. 6

   Prepare replacement brake line
   If using pre-flared line, verify correct length and fitting orientation. If fabricating custom line, cut nickel-copper or steel brake tubing to proper length using tubing cutter for clean, square cut. Deburr inside and outside edges. Create double flares on both ends using flaring tool according to manufacturer instructions. Flares must be perfect - any cracks or irregularities require re-cutting and re-flaring. Test fit fittings onto flares before installation.
7. 7

   Route and shape new brake line
   Route new line following exact path of original line, using your photos and notes as reference. Use tube bender to create any necessary bends - never kink the line. On Ram 3500 4WD, ensure line has adequate clearance from front differential, CV axles, steering components, and suspension travel limits. Line must not contact exhaust components or moving parts under any suspension position.
8. 8

   Install mounting clips
   Secure brake line with all original mounting clips in their original positions. Replace any broken clips with new ones. Clips must hold line firmly but not crush it. Verify line has no contact with frame, body, or moving components throughout full suspension travel. Shake suspension components to verify clearance.
9. 9

   Connect brake line fittings
   Thread both fittings onto their respective components by hand first to ensure proper thread engagement. Tighten with flare nut wrench until snug. Fittings should tighten smoothly without excessive force. If resistance is felt, back off and check for cross-threading or debris. Final tightening should follow the torque value specified in the factory service manual for the specific brake line fitting; typical brake tube nuts are torqued in the range of approximately 11-18 ft-lbs. Do not over-tighten as this can damage flares and cause leaks. Do not over-tighten as this can damage flares and cause leaks.
10. 10

    Bleed brake system
    Fill brake fluid reservoir to MAX line with fresh brake fluid meeting the specification marked on the reservoir cap (DOT 3 for 2007 Ram 3500). Bleed the system in the sequence specified in the factory service manual for the 2007 Ram 3500 (ABS-equipped). A scan tool may be required to bleed the ABS hydraulic control unit; consult the FSM for the correct wheel bleed order and procedure. Attach clear tubing to bleeder screw and submerge other end in container with clean brake fluid. Have assistant pump brake pedal 3-4 times and hold, then open bleeder screw 1/2 turn. Close bleeder before pedal reaches floor. Repeat until fluid flows clear with no air bubbles. Move to next wheel. Keep reservoir full throughout bleeding process - never let it run dry or you will introduce more air.
11. 11

    Inspect for leaks
    With system bled and pedal pumped to build pressure, inspect both new fittings carefully for any signs of brake fluid seepage. Wipe fittings dry with clean rag and have assistant apply firm, steady pressure to brake pedal for 30 seconds while you observe fittings. Any leakage requires immediate correction - do not drive vehicle with leaking brake lines.

Reassembly

1. Reinstall wheels if removed and torque lug nuts to specification (typically 135 ft-lbs for Ram 3500, verify in owner's manual)
2. Lower vehicle to ground
3. Fill brake fluid reservoir to MAX line with fresh DOT 3 brake fluid
4. Pump brake pedal repeatedly until firm pedal feel is achieved
5. Recheck brake fluid level and top off if needed
6. Clean any spilled brake fluid from vehicle surfaces immediately to prevent paint damage

Verification

• Start engine and pump brake pedal - pedal should feel firm and not sink to floor under steady pressure
• With engine running, apply firm brake pressure and recheck all connections for leaks
• Verify ABS warning light is not illuminated on instrument cluster
• Test brakes at low speed (under 5 mph) in safe area to confirm proper operation before road testing
• Perform test drive in low-traffic area, testing brakes at progressively higher speeds up to 25 mph
• Verify straight-line braking with no pulling to either side
• After 50-100 miles, recheck brake fluid level and inspect new line connections for any seepage
• Monitor brake pedal feel for first several days - any sponginess or pedal fade requires immediate re-bleeding or professional inspection

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