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FLK90/110/125 Cartridge

The innovative FLK filtration family is packed with all the latest hydraulic filtration advancements in a single package. The FLK system, a reusable aluminum head/housing with disposable filter cartridge, can also be configured with Donaldson’s advanced Synteq XP™ media technology – or with other Donaldson media offerings – to satisfy a wide range of performance requirements.


  • Hydrostatic Charge Pumps
  • Hydrostatic Transmission
  • Pilot Control Circuits


  • Choose FLK90, FLK110 or FLK 125 to meet system requirements
  • Excellent filtration performance – with many features that make it more convenient than other assemblies/filters
  • Robust, reusable housing and disposable cartridge design, create less waste than standard metal spin-on designs
  • Designed for easy, clean, convenient servicing
  • Short removal clearance makes the FLK design maintenance-friendly in tight spaces
  • RadialSeal™ design for reliable seal and superior vibration resistance
  • Synteq XP™ media, Donaldson's most advanced synthetic fiber media for greater filtration efficiency and higher dirt-holding capacity


  • High pressure fatigue ratings
  • Choose long or short housings/filters to meet capacity requirements
  • The oil drain port on the bottom of the housing and the locking grab handles on the filter cartridge allow for cleaner servicing
  • Industrial, raised hand grips for easy housing removal without tools
  • Filter tabs lock into place for easy positioning during reassembly
  • 4-point mount, optional 2-point mount
  • Heads feature one side machined/plugged for indicators
  • Working pressure to: 40 bar / 580 psi
  • Rated static burst to: 138 bar / 2000 psi
  • Flow range to: 151 lpm / 40 gpm
  • Porting size options:
    • SAE-12 O-ring
    • SAE-16 O-ring
  • Bypass ratings of:
    • 3.5 bar / 50 psi
    • No bypass

Available Media Types

  • Donaldson exclusive Synteq XP™ – synthetic fiber media for greater filtration efficiency and higher dust-holding capacity
  • Choice of efficiency grades
The following are recommended practices for hydraulic filter servicing and handling. These steps are universal to many hydraulic systems. This servicing information is provided as a best practices guide. Donaldson recommends that you follow the filter service instructions supplied by your original equipment manufacturer. These recommended practices are not intended to replace or supersede the service instructions supplied by your equipment or vehicle manufacturer.
  1. Check the filter service indicator
    Check to see that the OEM specified service interval has been reached or that the service indicator shows that the filter is due for servicing.

  2. Turn system off and release pressure
    Ensure that the hydraulic system is turned off.
    Check that there is no pressure present.

  3. Use oil drain port to better control oil removal from the housing 

  4. Unscrew the cartridge housing

  5. Remove the used filter and gasket, if applicable
    Properly dispose of the cartridge according to local regulations.

  6. Clean the head seal area and housing
    Clean out any sediment from the inside of the filter housing.

  7. Inspect the new filter cartridge for damage
    Check the new filter you will be installing for any shipping and handling damage. Do not install a damaged filter.

  8. Install and lubricate seals, gaskets and threads. 
    Lubricate the o-rings, gaskets, housing seals and threads with clean system oil.

  9. Install new cartridge into the housing

  10. Align threads. Spin filter until gasket contacts
    Fit the housing to the filter head as instructions on the housing.

  11. Install housing according to manufacturer instructions

  12. Bleed the hydraulic system and check for leaks

Donaldson Hydraulic Filtration Overview

Donaldson provides filters and contamination control products to protect hydraulic components -- in the factory and on heavy-duty equipment. This module provides an overview of hydraulic systems and the advantages of Donaldson hydraulic filters

Donaldson Hydraulic Filter Servicing

Donaldson provides best practices and recommended steps for hydraulic filter servicing. By following these simple steps, discover how you can reduce maintenance costs and extend the life of your hydraulic system.