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smlranger's avatar
smlranger
Explorer
Feb 09, 2014

Hydraulic fluid filter change question

My coach as a large, spin-on hydraulic fluid filter mounted outside the hydraulic fluid reservoir for the radiator fan and power steering. I want to change the filter and am wondering if I need to pre fill the new filter.

I is a fairly large, maybe 1 1/2 quart filter so I don't want to cause problems by putting it on dry.
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  • mtrumpet's avatar
    mtrumpet
    Explorer
    Feb 09, 2014
    If it's at the top of the reservoir, it's on the return line,(which BTW most Hydraulic filters typically are). No need to prefill it. It will get it's "fill" from the system since it's at the end of the "circuit" so to speak. But again, if you feel more comfortable pre-filling it, go right ahead. You won't hurt anything.
  • smlranger's avatar
    smlranger
    Explorer
    Feb 09, 2014
    Ok, I will just prefill it. I have a supply of cap plugs for filling fuel filters.

    My filter is mounted at the top of the reservoir so I guess there is some sort of dip tube inside to pull fluid from lower in the reservoir into the filter (assuming the filter is on the suction side of the PTO pump).
  • palehorse89's avatar
    palehorse89
    Explorer
    Feb 09, 2014
    smlranger wrote:
    My coach as a large, spin-on hydraulic fluid filter mounted outside the hydraulic fluid reservoir for the radiator fan and power steering. I want to change the filter and am wondering if I need to pre fill the new filter.

    I is a fairly large, maybe 1 1/2 quart filter so I don't want to cause problems by putting it on dry.

    If you pre-fill the new 1-1/2 quart filter.....chances are that your reservoir will not be 1-1/2 qts. low when done. Fill the new filter or add to the reservoir so to be at proper level when done.....
  • mtrumpet's avatar
    mtrumpet
    Explorer
    Feb 09, 2014
    As Brett eluded to, you can if you want to and it certainly wouldn't hurt anything, but not really necessary. Hydraulic systems are typically self purging of air. If in doubt, your best bet is to contact your chassis manufacturer (Spartan or Freightliner)directly.

    Here's some info that you might find helpful...

    TECH TIP: Installing spin-on hydraulic filters
  • CREATO's avatar
    CREATO
    Explorer
    Feb 09, 2014
    As stated if on suction side always fill the filter to prevent cavitation.
  • wolfe10's avatar
    wolfe10
    Explorer
    Feb 09, 2014
    Since most filters are on the suction side of the hydraulic pump, probably would not hurt.

    Fill the small outer holes (inlets) not center large hole (outlet).

    If the reservoir (actually oil level in reservoir) is above the filter base, you can also install dry, but not tighten the filter and let gravity fill it.

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