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NEWS | July 20, 2022

M109A7 Paladin, M992A3 Ammo Carrier: Avoid Damaging QDs

Mechanics, there have been hydraulic oil leaks where the quick-disconnect (QD) coupler, NSN 4730-01-657-6292, threads into the manifold, NSN 2590-01-652-4858, on the M109A7 Paladin’s and M992A3 ammo carrier’s cooling system plenum assembly.
 Manifold and quick-disconnect coupling on cooling plenum 
Manifold and quick-disconnect coupling on cooling plenum

Instructions for replacing the manifold, the QD coupler and the QD coupler’s O-ring, NSN 5331-01-006-9048, are in TM 9-2350-401-23&P (Nov 20). In addition to the instructions in the TM, be sure to also do the following: 
  • Clean the replacement manifold surface and check for damage prior to installation.
  • Clean the recessed area of the replacement manifold where the O-ring is seated and check this area for marring or rough edges.
  • Lubricate the QD coupler's threads with MIL-PRF-3150-02-PL-M, NSN 9150-00-231-2361, prior to installation
  • Lubricate the new O-ring with MIL-PRF-3150-02-PL-M prior to installing on the QD coupler.
  • After installing the QD coupler onto the manifold, tighten it to 120-130 lb-ft of torque.
Caution: Never operate the hydraulic system with the QDs disconnected. That can cause the female QD’s internal stem to fail.
It’s important to use care when connecting the quick-disconnects (QD) to their associated QD couplers or the internal O-rings could be damaged, causing hydraulic oil to leak at the QD. This is especially true for the hydraulic lubrication supply hose QD that connects to the plenum manifold QD coupler.
To prevent damage to the hydraulic lubrication supply hose QD when connecting it to the plenum manifold QD coupler:
  • Start the connection of the hydraulic lubrication supply hose QD by aligning it to the plenum manifold QD coupler in as close to perfect axial alignment as possible. Do not force parts together or jiggle couplings as internal damage may occur.
  • While holding the hydraulic lubrication supply hose and plenum manifold QDs together with the supply hose QD coupler’s collar retracted, rotate the fan(s) clockwise by hand to open the fluid path. Gently push the QDs together. The QDs should connect without having to apply extreme force.
  • After connecting the two (2) QD halves, pull on the hydraulic lubrication supply hose to verify they are connected properly.
Supply hose connection and rotational direction of fans
Supply hose connection and rotational direction of fans
Ground Hop Kit  

The ground hop kit, NSN 6110-01-659-0185, also uses QDs for connecting to the M109A7 and M992A3 powerpack. The following will help minimize damage to the QDs when connecting the ground hop kit to the powerpack:
  • Ensure all coolant and hydraulic hoses associated with the ground hop kit are fully connected to the powerpack before operating.
  • Follow proper QD connecting technique to be certain that:
    1. the slots on the female QD align with pins on male QD.
    2. the female and male QDs are carefully pushed together and rotated in a clockwise direction so the QDs lock together.

For more info, check out TACOM Maintenance Information Message 22-040 HERE.
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