Air Line

Complete replacement of the compressed air lines in the air brake system, including inspection of fittings, routing new lines, and pressure testing for leaks.

Warnings

Tools required

Parts

• 3/8" OD copper-nickel brake line tubing × 1 — Length as needed, typically 25-50 feet
• 3/8" tube nuts (inverted flare) × 8 — Use OEM specification or SAE J512
• Inline air filter (if equipped) × 1 — Use OEM specification
• Air line mounting clips × 12 — Ford C5TZ-18A461-A or equivalent
• Compression fittings (if used) × 4 — 3/8" NPT to 3/8" tube
• Teflon tape × 1 — High-pressure rated
• Thread sealant (pipe dope) × 1 — Permatex 80631 or equivalent

Preparation

1. Park vehicle on level ground and set parking brake firmly
2. Chock front wheels securely
3. Raise rear of vehicle and support on jack stands at frame rails
4. Locate air compressor and identify all air lines to be replaced
5. Turn off air compressor (if electric) and disconnect power
6. Open all air system bleed valves or disconnect lines at compressor to release pressure completely
7. Allow system to depressurize for at least 5 minutes and verify zero pressure with gauge
8. Take photographs of existing line routing and connection points for reference

Procedure

1. 1

   Remove existing air lines from compressor
   Starting at the air compressor, use flare nut wrenches to disconnect the air lines from the outlet ports. The compressor typically has 2 outlet fittings. Remove the main supply line first, then secondary lines. Cap or plug compressor outlets immediately to prevent debris entry.
2. 2

   Trace and disconnect lines at brake canisters
   Follow each air line to the air tanks, air suspension bags, or air accessory components. If this is an air-over-hydraulic system, locate the air chambers or boosters mounted to the frame or axle housing. Use flare nut wrenches to disconnect the lines at the canister inlet fittings. The number of connections depends on the specific aftermarket air system installed (commonly 2 for a rear-axle-only setup, more for four-wheel). Verify actual count on this vehicle. Cap all open fittings.
3. 3

   Remove mounting hardware and old lines
   Work along the frame rails and locate all mounting clips securing the air lines. Remove all mounting clips along the routing path (count varies by installation) using appropriate tools. Carefully remove the entire length of old air line, inspecting routing path and noting any frame penetrations or grommets that must be reused.
4. 4

   Inspect all fittings and components
   Thoroughly clean all connection points with brake cleaner. Inspect compressor outlet threads, brake canister inlet threads, and any inline components (filters, pressure switches, check valves) for damage, corrosion, or stripped threads. Replace any damaged fittings or components before proceeding.
5. 5

   Measure and cut new tubing for main supply line
   Using the old line as a template, measure the required length for the main supply line from compressor to the first junction or brake canister. Add 6 inches for bending and flaring allowance. Cut the 3/8" tubing (verify DOT/pneumatic-rated air line material) squarely using a tubing cutter. Deburr the cut end thoroughly inside and outside.
6. 6

   Form double flares on main supply line
   Install the appropriate tube nut onto the tubing before flaring. Using the double flare tool, create a double inverted flare on each end of the main supply line section. Ensure flares are concentric, smooth, and fully formed without cracks. Test fit the flare into a spare fitting to verify proper seating.
7. 7

   Bend and shape main supply line
   Using the tubing bender, carefully form the necessary bends to route the main supply line along the frame rail from compressor to the first connection point. Make all bends smooth with minimum radius of 3 inches to prevent flow restriction. Avoid kinks or flattened sections.
8. 8

   Install main supply line to compressor
   Apply Teflon tape or thread sealant to any NPT threaded fittings at the compressor outlet. Thread the tube nut onto the compressor fitting and hand-tighten. Using flare nut wrench, tighten the connection snugly without over-torquing (typically 15-25 ft-lbs for 3/8" flare fittings, but hand-tight plus 1/4 turn is sufficient without a torque wrench).
9. 9

   Measure, cut, flare, and bend secondary air lines
   Repeat the measuring, cutting, deburring, tube nut installation, double flaring, and bending process for each remaining air line section. Typically this includes 1 line from the main junction to each rear brake canister. Ensure each line follows the original routing path and maintains adequate clearance from exhaust, suspension, and drive shaft components.
10. 10

    Install all secondary lines to brake canisters
    Connect each air line to its respective brake canister inlet fitting. Apply thread sealant to NPT threads if present. Hand-tighten all connections, then snug with flare nut wrench. Verify each line has smooth routing without sharp bends or contact points that could cause chafing.
11. 11

    Secure lines with mounting clips
    Install new mounting clips along the frame rails at approximately 12-18 inch intervals. Position clips to support the lines without crushing or deforming the tubing. Ensure adequate clearance from moving suspension components, exhaust system, and drive shaft throughout full suspension travel.
12. 12

    Install inline filter and accessories
    If the system includes an inline air filter, pressure switch, or check valve, install these components in the correct sequence and orientation. Apply thread sealant to all NPT connections. Ensure the filter is positioned with the flow direction arrow pointing toward the brake canisters.
13. 13

    Perform initial pressure test
    Close all bleed valves. Reconnect compressor power (if electric) or prepare to manually charge system. Slowly bring system pressure up to 30 PSI and hold. Spray all connections, fittings, and flares with soap solution and observe for bubbles indicating leaks. Repair any leaks before proceeding.
14. 14

    Complete full pressure test
    Gradually increase system pressure to the normal operating pressure for your specific aftermarket air system (typically 50-100 PSI for air suspension, 100-150 PSI for air horns or air accessories, or per manufacturer specifications). Allow pressure to stabilize for 5 minutes. Re-check all connections with soap solution for leaks. System should hold pressure without any loss for at least 10 minutes. Address any leaks immediately.
15. 15

    Final inspection and road test preparation
    Remove jack stands and lower vehicle to ground. Perform a final visual inspection of all air lines, verifying secure mounting, proper routing, and no contact with moving parts. Cycle the brake pedal several times to verify air assist operation. Check system pressure gauge returns to normal after brake application.

Reassembly

1. No disassembly of other components required for this procedure
2. Ensure all mounting clips are secure and lines are properly supported
3. Verify air compressor is reconnected and operational

Verification

• System holds full operating pressure (90-120 PSI) for at least 10 minutes without loss
• No air leaks detected at any connection point using soap solution test
• Brake pedal feel is firm with normal travel when air system is pressurized
• Air compressor cycles on and off properly to maintain system pressure
• All air lines have adequate clearance from exhaust, suspension, and driveline with suspension at full compression and extension
• Perform test drive and verify normal brake operation with air assist functioning properly

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