Ph: (07) 3881 0384 Print this page

Filter Cleaning Article

Ross Leach, Brisbane Air-Cleaner Services a Veteran of servicing Air  Filters
with 23 years experence

Unfortunately, very little has been written on air cleaner servicing and what has been written is hidden within owner's manuals never to be read. The fact of the matter is that most air elements are over-serviced, purely because operators lack knowledge of how an air element works in its environment. Sometimes others who also do not understand have misguided them. 

Firstly, let’s explain how an air cleaner works and why it is made like it is. Most air cleaner housings are made cylindrical and are fitted with a pleated paper element.
We will take the air-housing first.
Most modern air-housings are of a two-stage design with the first stage precleaning the air with the aid of cyclonic action. Inspecting the inside of the air-housing can identify this. If it is a true cyclopac, either the element or the air-housing will be fitted with fins to swirl the air complete with contaminates. The heavier contaminates will be flung to the outer wall and be carried to the vacuator valve or the dust bowl at the end of the housing.
If the air cleaner is not of this type it is unfortunate because the element will have to contend with the job of removing all the contaminates which in turn will shorten the service life of the element.
The second stage of the cyclopac is to filter the air via the element.

The element is made of resin treated paper primarily because of economics and compactness.

There is a lot better filter media than paper but paper elements can do the job of protecting your engine if they are serviced correctly


Now let us look at the paper in an element. To explain, let us say the paper is made up of three layers. The inner layer being a fine matrix of paper fibers which forms a membrane to do the final filtering until the air element establishes itself.


The middle layer is of courser construction than of the inner layer same as the outer layer is of the middle layer. With this type of arrangement of paper fibers, dirt particles can be caught in such a manner so as they will not restrict the passage of air through the element.


Now, here comes the bit nobody seems to understand. When the paper fiber load up with dust, etc. the outer layer of paper starts to build up with more dust, etc. This is now the time when the filter (paper + dust etc.) is just starting to be efficient at filtering the air to the engine. Sure, one could say it will be more restricted and they would be right in saying so, but the design of the air cleaner (properly sized for the job) will handle this easily.

From this point, the filter element with its precoat of dust, etc. is just starting to do its job efficiently. As the layers build, the element is better as a filter but there comes a time to service it. It is a proven fact from tests carried out by the larger filter manufacturers that 70% of the dust which an air element will emit to the engine will occur in the first 30% of a filter’s service life.

So, when you get the air nozzle onto an air element you are guilty of blowing away the best part of your air-filtration system. Now, here comes the tricky bit.

Most operators look at the filter and say, “it's dirty”, but how dirty is it? Well, one thing is for certain; nobody can tell what the condition of the filter is unless the air-housing is fitted with a reliable restriction gauge.

Let us digress at this point. Every operator uses gauges to monitor the engine's condition such as water, temperature, oil pressure, etc. and understands what they are telling them but most operators do not even realize what the true job of the restriction gauge (if fitted) is telling them or in fact why it is there or if there is one fitted.

Air restriction gauges come in four basic types. A: simple plastic type which shows red when element has reached max restriction as per gauge setting. B: similar to A but shows restriction in graduated steps. C: dash light, which lights when max preset restriction is reached. D: dash mounted vacuum gauge. Unit B & D are the better types because they give you forward warning of rising restriction of the air cleaner element.

Now, let’s get back to servicing the air cleaner element. If the element installed is new, it is best checked early in its life to see if any dust trails are evident inside the clean-air side of the paper just in case of faulty manufacturing. Remove the element and inspect it and check the outlet side of the air cleaners' plumbing. If inspection reveals no evidence of leakage then replace the element without bumping or blowing it with air. That is all the servicing it will require from time to time until the service restriction gauge indicates its time for change. Depending on what type of equipment the air cleaner is fitted to you may need to vary the changeover time of the element.


Trucks (around town haulage): Have element washed every 6 months or when gauge indicates, whichever is the sooner. The reason being that local haulage is in a very sooty environment and if element is allowed to work too long with this type of road grime on its paper surface it will be harder to clean and will have a shorter reusable life.

Trucks (long-haul highway): Run element until restriction gauge indicates service change or 12 months whichever the sooner.

Earthmoving Equipment: Run element until restriction gauge indicates service change or 6 months whichever the sooner.


If operating in very moist conditions and indicator shows time for change it may be only that element is wet which will make it much more restrictive. In these conditions change element for a dry one and dry wet element for reuse later to enable you to receive maximum service life from the element.

Hoping the above information will assist you in the understanding of your air-cleaner and its servicing.

Updated Wed 9 May 2012 2:27pm

Previous page: Articles
Next page: Customer Filter Cards