Hydraulic filters are the Bouncers of your hydraulic system. As the main defence against contamination, they dictate who and what get’s through.

Understanding how to maintain and replace these filters is critical. Neglecting them can lead to bad things, including catastrophic system failure.

Let’s look at a step-by-step approach to hydraulic filter replacement, explaining the "what," "why," and "how" of this essential maintenance task. By the end, you'll be a hydraulic filter expert – and in doing so, be able to keep your equipment running at peak performance.

The Role of Hydraulic Filters

At its core, a hydraulic system relies on clean fluid to transfer power. However, like any fluid, it can become contaminated with particles from internal wear, like metal shavings or external sources like dust, dirt and general Aussie grime. 

Left alone, that contamination turns your oil into liquid sandpaper, slowly grinding your pumps, valves and cylinders.

The result:

• Sluggish performance

• More pressure needed to do the same work

• Heat, noise and eventually something goes “bang” and everyone pretends they didn’t hear it

Hydraulic filters are there to catch the particles before they destroy the expensive bits. Small, boring and absolutely critical.

Types of hydraulic filters (and what they’re protecting)

Think of your hydraulic circuit like a pub with multiple security checkpoints.

Suction filters – the front‑door bag check

Sitting between the tank and the pump, suction filters (or strainers) stop the big chunks before they ever touch the pump.

• Low‑pressure, usually wire mesh

• Their main job: keep rocks, rag offcuts and “mystery bits” out of the most expensive component in the system – the pump

Pressure filters – the VIP bodyguards

These live downstream of the pump, looking after your high‑value components like control valves and actuators.

• Designed to handle full system pressure (well into the thousands of psi)

• Catch fine particles generated inside the system or anything that snuck past the suction filter

Return filters – the clean‑up crew (and often the MVP)

These sit in the return line on the way back to the tank.

• Their job: scrub the oil clean before it dumps into the reservoir

• They catch wear particles from cylinders, motors and valves as the oil comes home

• Because they “polish” the oil before it hits the tank, Flotek Technicians consider the return filter the most important filter in the system

In‑tank and breather filters – the quiet achievers

• In‑tank filters: live inside the reservoir, often on the return line, saving space and simplifying plumbing

• Breather filters: sit on the tank vent and stop the outside world (dust, moisture, Melbourne’s finest construction‑site air) getting sucked into the system as the oil level goes up and down

Ignore these and you might as well leave the tank lid off in a dust storm.

How to change a spin‑on hydraulic filter (without making a massive mess)

Spin‑on filters are the classic “oil‑filter‑style” units – easy enough to replace if you follow a process and don’t rush it.

1. Set up properly)

• Park the machine on level ground

• Shut it down and make sure the hydraulic system is depressurised (no one wants a surprise high‑pressure oil shower)

• Drop an oil drain pan or tray under the filter – hydraulic oil has a way of finding clean concrete

2. Remove the old filter

• Use a filter wrench to crack it loose, turning counter‑clockwise

• Once it’s loosened, spin it off by hand

• Keep it upright as you lower it – the less oil you spill, the fewer rags you burn through

3. Clean the filter head

• Wipe the mounting surface with a clean, lint‑free rag

• Make sure there’s no old gasket stuck on there (double‑gasketing is the fast track to a nasty leak)

• Remove any dirt, grit or old oil – a clean surface is your best defence against annoying dribbles

4. Prep the new gasket

• Take the new filter, find the rubber gasket/O‑ring

• Smear a thin film of clean hydraulic oil around the seal

• This helps it seat properly and avoids tearing or twisting as you tighten it

5. Install the new filter

• Spin it on by hand until the gasket just makes solid contact with the filter head

• Then tighten it a further half to three‑quarters of a turn – or exactly as per the manufacturer

• Do not go full Hulk and overtighten – you’ll wreck the seal or distort the housing

Fire up the machine afterwards and check for leaks. If it’s dry after a few minutes under load, you’ve done the job right.

What happens when filters clog

Over time, filters do their job and load up with contamination. That’s normal.
What isn’t normal is leaving them in so long that:

• Flow gets restricted

• The system has to work harder

• Temperatures rise and everything gets stressed

And by-pass isn’t your friend…

To stop the system starving for oil, many pressure and return filters have a bypass valve.
When the filter is too clogged:

• The bypass pops open

• Oil flows around the filter instead of through it

• You keep working… but now with unfiltered, dirty oil racing through your system

So yes, the machine still moves, but every minute it’s running in bypass, is costing you money in a future rebuild.

Best practice for filter maintenance (Aussie conditions in mind)

1. Follow the manual (mostly)

• The manufacturer’s intervals are your starting point

• Typical guide: change filters when you change the oil, often around 1,000–2,000 hours in decent conditions

2. Adjust for real life (dust, mud, quarries, Melbourne sites…)

Australian worksites are rarely “clean room” conditions. If you’re:

• Working in dust, demolition, quarries, land clearing, farm paddocks, or building sites around Melbourne’s west

• Regularly swapping attachments or opening the system

Reducing intervals to around 600–800 hours for key filters is smart.

3. Inspect regularly

• Check filters for dents, corrosion or deformities

• Keep an eye on any pressure indicators or gauges across the filter – rising differential pressure is your early warning that the element is loading up

• If you’re using a service provider like Flotek for quarterly inspections, make sure filter condition and bypass indicators are specifically checked and noted in the report

4. Use the right filter

It sounds obvious, but it’s one of the most common sins:

• Match the pressure rating to the circuit – low‑pressure element in a high‑pressure line = bad day

• Match the micron rating and efficiency to the OEM spec – too coarse and you may as well not bother

• Going for a bargain‑basement element usually saves tens of dollars and risks thousands – classic false economy

Final Thought

Hydraulic filters are Small, boring and absolutely critical. They don’t get the plaudits of the high-profile components in a hydraulic system get. However, without them, your machine won’t be working for too much longer. Flotek technicians pay close attention to filters, and replace anything that looks like it’s going to lead to a bigger problem down the track. Filters are a hydraulic systems least expensive, but most effective insurance policy.