4WD Air Filters

In a daily driven town car, air filter maintenance seems a fairly low priority. It’s not until you take your 4WD into the dusty environs of rural Australia that an air filters importance takes on a new dimension.

There are three major maintenance events required to maximize engine longevity. The ‘holy trinity’ if you like.

  1. Fresh Oil is an absolute essential. Quality oil and filters require changing at manufacturer’s recommendations or sooner in harsh conditions
  2. Clean Fuel, easily achieved by changing filters as recommended and using clean fuel to begin with.
  3. Clean Air is often overlooked as part of a regular maintenance schedule. Air is the third element, after oil and fuel, that is ingested by an engine.
Longevity
paper barrel type air cleaner

By supplying an engine with these three items at the required intervals it is possible to achieve 500,000km from an engine without a rebuild. Taxis running on gas easily achieve a million kilometres, diffs, gearboxes and seats wearing out long before motors do. We have seen 75 series landcruisers on cattle stations with a million kilometres on them. They are definitely not the sort of vehicle you want to spent large amounts of time sitting in but they still go.

Once your four wheel drive hits the highway it starts to rack up serious mileage. If it’s towing a boat or caravan then it is working even harder than normal and if it’s being driven on gravel roads then it’s potentially sucking a lot of dust.

There are a couple of things you can do to help with minimizing dust inhalation by your engine. Snorkels can make a difference by lifting the air intake up out of the general plane of contaminants. An article about snorkels can be seen here.

Prevention

If you are travelling in convoy then allow a large margin between vehicles. It may sound like common sense, but apart from being more relaxed and safer, a distance of up to a couple of kilometres between 4WD’s means staying out of the dust.

The first line of defence against dust for the engine of your car is the air filter. Most vehicles come supplied with a cartridge type disposable paper filter although some manufacturers of modern 4WD’s have begun to supply a ‘washable’ type filter to help reduce maintenance costs.

With the price of a modern 4WD air filter upwards of a $100 and requiring changing at 15000km to 2000km it’s tempting to source an alternative.

Foam filters have been around for a long time. Offroad Motorcycles still come equipped with foam filters and cleaning and re-oiling the filter is part of daily racing maintenance for motocross or enduros.

The manufacturers of foam filters claim better airflow – meaning better performance, better restriction of contaminants through the filter and cheaper running costs. While choosing to use a foam filter and washing it and re-oiling it will definitely be cheaper in the long run, the benefits are only as good as the quality of the maintenance job itself.

Too much oil sees the filter become restricted and unable to pass adequate air to the engine. This in turn can cause havoc with air/fuel sensors or may cause the car to run rich, consuming more fuel.

Too little oil and protection is diminished allowing contaminants to pass through the filter.

Large earthmoving manufacturers like Caterpillar and the majority of earthmoving companies still use disposable paper filters on their million dollar equipment.

Sealing

Good practice is to check all the sealing points on the air intake system, beginning with the snorkel or air intake line and working back to the airbox and filter itself. Leaks and damaged seals in these areas mean even the newest of filters could be rendered useless.

Airbox lids are a particular concern and every effort should be made to ensure tight, leakless sealing.

The application of a bead of grease on bottom and top seals of the filter itself go a long way to creating the sort of vacuum you are trying to achieve through the filter airline.

When travelling on long dusty roads the lifetime of the air filter can be reduced from around the 20,000km to as low as a couple of thousand kilometres. Mileage is irrelevant, what is crucial is the amount of dust the engine could potentially be ingesting.

Daily checks can be made and the internal throat of the airbox inspected to see if any dust is passing the filter. This is also a good opportunity to ‘tap out’ any dust trapped in the filter. Mine sites and earthmoving companies once ‘blew out’ the air filters of large excavation machinery. This was conducted on a daily basis with compressed air, blowing the filter from the inside out. This is frowned upon these days due to health and environmental concerns. It is however, amazing how much dust can be trapped by a single filter in a single day.

Schedules

There are no rules regarding filter changes in dusty conditions and judgement and experience are your best guides. If your manufacturer recommends 20,000km changes then consider that the upper limit for bitumised town driving. As soon as you take the vehicle into the dirt be aware of the volume of dirt you may be ingesting and act accordingly. If you can see dirt in the throat of the airbox or contaminants have worked their way into the inner ring of the filter then the maintenance cycle needs upgrading.

We use oiled foam filters on motorbikes and paper filters in 4WD’s. Pre-filters can be effective when used in the mouths of snorkels in extreme dust.

Some aftermarket filters look identical to the genuine units and come at a considerable saving. It must be remembered that the use of a non genuine air cleaner will almost certainly cause a dust related warranty claim to be voided.

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