Air Line

This procedure covers the replacement of air brake lines on a 1994-2007 Dodge Ram 2500 4WD with the 5.9L Cummins diesel engine, including removal, installation, and bleeding of the brake system.

Warnings

Tools required

Parts

• Brake line (appropriate length and diameter) × 1 — Use OEM specification 3/16" or 1/4" steel line
• Brake line fittings (if applicable) × 2 — Use OEM specification
• Brake line clips/brackets × 3 — Use OEM specification

Fluids

• DOT 3 brake fluid — 1 qt

Preparation

1. Park vehicle on level surface and place wheel chocks behind rear wheels
2. Open hood and locate brake fluid reservoir; note current fluid level
3. Raise vehicle using floor jack and support securely on jack stands at frame rails
4. Remove wheel(s) on side where brake line is being replaced using 3/4" socket
5. Identify the specific brake line to be replaced (front-to-rear hard line, flex hose to caliper, etc.)
6. Apply penetrating oil to all brake line fittings and allow to soak for 10-15 minutes
7. Place drain pan under work area to catch brake fluid

Procedure

1. 1

   Disconnect battery negative terminal
   Disconnect the negative battery terminal to prevent accidental ABS system activation during the repair. This is especially important on models equipped with ABS. Use a 10mm wrench to loosen the terminal clamp and move the cable away from the battery post.
2. 2

   Remove damaged brake line section
   Using line wrenches, carefully loosen and disconnect the brake line fittings at both ends of the damaged section. Start with the upstream fitting (closer to master cylinder) first to minimize fluid loss. Hold the component fitting stationary while turning the line nut to prevent damage to the component threads. Allow brake fluid to drain into the pan. Use line wrenches rather than open-end wrenches to prevent rounding off the brake line fittings. OEM hydraulic brake line fittings on this vehicle are steel, not brass. Brass is used on some aftermarket adapters but the factory hard-line fittings are steel.
   ⚠Use line wrenches rather than open-end wrenches to prevent rounding off the soft brass fittings.
3. 3

   Remove line mounting clips and brackets
   Locate and remove all mounting clips, brackets, and retainers securing the brake line to the frame, body, or suspension components. These are typically held with 8mm or 10mm bolts or plastic push clips. Note the routing path and clip locations for proper reinstallation.
4. 4

   Extract old brake line
   Carefully remove the old brake line from the vehicle, taking note of its routing path, bend angles, and clearance from moving components like the driveshaft, steering linkage, and suspension. Take photos or measurements for reference during installation of the new line.
5. 5

   Prepare new brake line
   Measure and cut the new brake line to the appropriate length, adding 1-2 inches for flaring. Use a tube cutter for a clean, square cut. Remove any burrs from the cut end with a deburring tool or fine file. Ensure the line is clean inside and out before flaring.
6. 6

   Flare brake line ends
   Install the appropriate fittings on the line before flaring. Create double-flares on both ends of the brake line using a flare tool kit. Ensure flares are even, smooth, and properly seated in the flare tool to prevent leaks. The flare should be centered and free of cracks or splits.
   ⚠Improper flares are the most common cause of brake line leaks. Take time to create quality flares.
7. 7

   Bend and shape brake line
   Using a tube bender, carefully bend the new brake line to match the routing path of the original line. Make smooth, gradual bends without kinking the line. Ensure adequate clearance from the driveshaft, exhaust components, and suspension travel points. Test-fit the line before final installation.
8. 8

   Install new brake line
   Route the new brake line along the frame following the original path. Start by threading the fittings at both ends finger-tight before securing any mounting clips. Ensure the line has proper clearance from all moving and hot components. Verify that the line is not twisted or under tension.
9. 9

   Install mounting clips and brackets
   Install all mounting clips, brackets, and retainers in their original locations. Tighten mounting bolts to specification if using threaded fasteners (typically around 7-17 lb-ft depending on bolt size). Ensure clips hold the line securely without crushing or deforming it. The line should be well-supported but not restricted from minor movement.
10. 10

    Tighten brake line fittings
    Using line wrenches, tighten both brake line fittings. Start with the upstream fitting (closer to master cylinder). Hold the component fitting stationary with one wrench while tightening the line nut with another. Tighten firmly (typically 10-15 lb-ft) but do not over-torque as this can strip the threads or damage the flare seat.
    ⚠Over-tightening brake line fittings can damage threads and flare seats, causing leaks. Tighten until snug, then add 1/4 turn.
11. 11

    Bleed brake system
    Fill the brake fluid reservoir to the MAX line with fresh brake fluid meeting the specification stamped on the reservoir cap (typically DOT 3). Starting with the wheel furthest from the master cylinder (typically right rear), attach clear tubing to the bleeder valve and submerge the other end in a container of brake fluid. Have an assistant pump the brake pedal 3-5 times and hold pressure. Open the bleeder valve to release fluid and air, then close before releasing pedal. Repeat until fluid flows clear without air bubbles. Proceed to remaining wheels in sequence (left rear, right front, left front).
    ⚠Never let the brake fluid reservoir run empty during bleeding or air will enter the system.
12. 12

    Inspect for leaks
    With the system bled, have an assistant apply firm, steady pressure to the brake pedal while you inspect all new fittings and connections for signs of leakage. Wipe fittings dry, then observe for any seepage. Check that the pedal remains firm and does not slowly sink to the floor.
13. 13

    Reinstall wheels
    Reinstall the wheel(s) that were removed. Hand-thread all lug nuts first, then tighten in a star pattern to ensure even seating. Use a torque wrench to torque lug nuts to specification in a star pattern.
    Torque spec

    Wheel Lug Nuts183 Nm (135 lb-ft)
14. 14

    Final system check
    Lower vehicle to the ground. Reconnect the negative battery terminal. Top off brake fluid reservoir to the MAX line. Start the engine and pump the brake pedal several times to build pressure. The pedal should feel firm and return to normal height. If equipped with ABS, the ABS pump may cycle once or twice after starting.

Reassembly

1. Ensure all brake line fittings are tight and free from leaks
2. Verify brake line routing has adequate clearance from suspension, driveshaft, and exhaust components
3. Confirm all mounting clips and brackets are installed and secure
4. Top off brake fluid reservoir to MAX line with fresh DOT 3 fluid
5. Clean any spilled brake fluid from vehicle surfaces immediately to prevent paint damage

Verification

• Start engine and verify brake pedal is firm with approximately 1-2 inches of travel before resistance
• Perform a stationary brake test: apply firm pedal pressure and hold for 30 seconds to verify pedal does not sink
• Test drive vehicle in a safe area at low speed to verify proper brake operation and pedal feel
• Perform several moderate brake applications from 15-20 mph to seat the system
• Re-inspect all new brake line connections for any signs of leakage after test drive
• Verify brake fluid level in reservoir remains at proper level after test drive
• If equipped with ABS, verify the ABS warning light extinguishes after initial system check

More procedures for this vehicle