2004 Freightliner XC Chassis
Air Dryer Filters Replacement
Haldex Pure Air Plus
Skills Required: Strong arms to unscrew canister,
Parts Required: Haldex DQ6026 kit, about $130.
Equipment Required: Large filter strap wrench,
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 a 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.
  6. The Pressure Relief Valve (2) can actually be removed 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.
  7. Open the strap clamp (3) fully using the 3/8" tall socket.
  8. The assembly will still be connected by two air hoses, but it 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. Reach inside and pull out the white Coalescing Filter by pulling on two of the four plastic tabs.
  10. Install the new o-ring on the new Coalescing Filter, apply silicone grease, 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 for
    now.
  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. 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. Tighten Desiccant Canister (1) pretty much as far as you can go with the strap wrench around
    the base.
  18. Remove the three screws holding the old Purge Shield (6). 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.
  19. 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.
  20. Remove single Pipe Plug (7) using 5/16" Robertson bit, drain contaminants if any, apply pipe
    sealant to threads of plug, and reinstall, tightening to 12 lb-ft torque.
  21. 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.
Back To Main Discovery Page
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 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