2004 Freightliner XC Chassis
Air Dryer Filters Replacement
Haldex Pure Air Plus
Skills Required: Strong arms to unscrew canister,
    strong hands to reconnect clamp.
Parts Required: Haldex DQ6026 kit, about $130.
    (smaller kit DQ6022 no longer available)
Equipment Required: Large filter strap wrench, pliers,
    small torque wrench, the following sockets: 5/16", tall 7/16",    
    9/16", tall 11/16"; regular ratchet, small flat-head screwdriver,
    9/16" open end wrench, paper towels, degreaser spray, latex
    gloves. Optional: (rare) 5/16" square (Robertson) bit and pipe
    sealant (see step 19).
Time Required: At least 2 hours first time.
  1. Release all air from system using three halyards located near passenger side of generator base.
  2. Loosen large Desiccant Canister (1) using the filter strap wrench, but do not remove yet because
    there is insufficient clearance at top and the likelihood of grime falling down from the overhead
    wiring. Expect to use a lot of force but make sure you turn clockwise looking from underneath.
  3. Remove the small air line (4) using the 9/16" open end wrench after removing grime from around
    it.
  4. Disconnect the heater wire connection (8) by lifting the locking tab slightly on one side and
    pulling.
  5. Remove the bracket bolt (Cap Screw in the DQ6026 instructions) on the bottom of the assembly
    (5) using the 9/16" socket or wrench.
  6. The Pressure Relief Valve (2) could be removed at this stage by slipping a box end 11/16"
    wrench over the end and removing the valve and wrench together, but it would be easier to
    remove with a socket as shown below in step 12.
  7. Before loosening the strap clamp (3), count the visible threads on the nut end so it can be
    returned to the same tightness afterwards. Remove the nut completely using the 7/16" tall socket.
  8. The assembly will still be connected by two air hoses, but can be gently pulled down and tilted
    forward to allow easy removal of the Desiccant Canister and visual inspection of the cavity, after
    cleaning around the outside of the old filter first.
  9. Pull out the white Coalescing Filter by prying up one of the four plastic tabs with the pliers.
  10. Install the new o-ring on the new Coalescing Filter, apply silicone grease (supplied with the kit),
    and insert. Be sure to push it all the way down like the old one.
  11. Apply silicone grease to the large Desiccant Canister outer seal and then screw on hand tight,
    after making sure the mating surface is completely clean.
  12. Remove the old Pressure Relief Valve (2) if you haven't already, and install new one using 11/16"
    socket to 15 lb-ft torque.
  13. Replace entire assembly back onto the lower bracket and reinstall bolt (5) using 9/16" socket to
    30 lb-ft torque.
  14. Reconnect strap clamp (3) and tighten to 6 lb-ft (or to the same thread depth as before). Be
    careful not to get air hose or heater wires under the clamp.
  15. Reconnect small air hose (4) using 9/16" open end wrench.
  16. Reconnect heater wiring (8).
  17. Remove the three screws holding the old Purge Shield (6) with the 5/16 socket. Use the flat-
    bladed screwdriver to pry the shield gently around the edges, a little bit at a time because it's
    stuck on and fragile.
  18. Replace shield gasket, new plastic shield, and metal plate. Torque screws to 3 lb-ft after making
    sure the heater and gasket are resting loosely underneath the shield.
  19. Directions with the kit call for removing the Pipe Plug (7) using a 5/16" Robertson bit, draining
    contaminants if any, applying pipe sealant to threads of plug, and reinstalling to 12 lb-ft torque.
    But if the filters are clean and dry, I'd suggest skipping this step and not risk introducing metal
    and sealant debris.
  20. Power air system back up. Test front halyards for sticking valves from prior dump operation.
    After system airs up fully, turn system off and verify no air leaks from replaced components.
Note: This is what 3-1/2 year old
filters can look like when only
operated in dry climates: almost new.
Your mileage may vary. If your
filters look gummed up, you need to
shorten your replacement interval.
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The instructions in the Freightliner Recreational Vehicle Chassis Maintenance Manual are an
overview only and don't reflect the procedures required after structures have been positioned
over the bare chassis. The DQ6026 kit comes with a comprehensive instruction sheet, but
contains some errors. Read through all information there, especially the safety precautions. If
in doubt, follow those instructions, but the following procedure will be easier to follow and
perform, given the typical Haldex installation in a motorcoach Freightliner XC chassis.
1. Desiccant Filter
2. Pressure Relief Valve Assembly
3. Strap Clamp
4. Small Air Hose Connection
5. Bracket Bolt (Cap Screw)
6. Plastic Purge Shield
7. Single 3/8" Pipe Plug
8. 12v Heater Connector