There’s a range of modern 4x4’s on the market suffering from dust ingestion issues, mainly those with a panel type air filter such as:
Toyota Land Cruiser 76/78/79 & 200 series, Toyota Prado 150 Series, Toyota Hilux GUN 122,123,125 & 126 Series, Nissan Navara D40 & D23, Mitsubishi Triton ML-MQ, Isuzu D-Max TF Series to name just a few.
The main reason for the dust issues on all these vehicles is the sealing edge of the filters. Rubber seals on plastic are not the best option when used in dusty conditions. Plastic air boxes warp out of shape when they heat up. Rubber does not warp the same way. As a result the rubber seal does not compensate for the plastic going out of shape. This is the reason all dirt bike filters are foam air filters with foam seals. The foam seal takes up the slack when the box air box warps. To fix the sealing issue on the Toyota Land Cruiser and Prado models we have added a foam seal to the sealing edge of the rubber seal. The sealing edge of these filters is flat so we can add a special foam seal that doesn’t breathe, so dust will not penetrate it.
The other style of panel filters use a step style seal. These filters use a small contact point to seal on the air box. This is fine on road going car where dust is not and issue. On a 4x4 the dust will find its way past this point easily as the air box heats up. Due to the style of the seal we cant use foam to help with the sealing of the air box. To help improve the seal on these filters we have widened the sealing edge and made it flat rather than a point to spread the sealing point. We also make these filters ridged so they cant deform under load like the O/E style filters.
Our panel filters use two layers of foam. The outer layer is the work stage and the inner layer is a back up stage. Effectively it’s two filters in one. Foam is also the best filtering material for dusty conditions. When the correct oil is used on foam filters they will continue to breath and filter, even when dirty.
You can also buy spare foam inserts for when you are traveling. This allows you to simply replace the inserts, bag the dirty ones up to clean when you get home. They take up very little room in your vehicle.
Oiling and Cleaning foam air filters correctly is very important. Only use foam air filter oil when oiling foam air filters. Oil designed for Cotton air filters is NOT suitable. Only use oil that comes in a plastic bottle and is thick in consistency straight out of the bottle. Never use spray oils or oils that go on like water and then become tacky. These oils will shorten the like of the foam.
When cleaning only use Mineral turpentine or Unifilter’s Citrus Cleaner. Petrol, Kero & Metho etc will shorten the life of the foam.
Using a sealing grease around the filter sealing edge is also a good idea. We recommend using regular bearing grease. Some rubber sealing greases have chemicals in them that can affect the sealing foam.
Unifilter also manufactures a large range of snorkel pre-filters. These are a great addition when going off road and especially if travelling in convoy. Pre-cleaner are designed for use when its dusty. They can be used in normal driving conditions with out affecting performance but to get a longer life out of them we only recommended using them when the conditions require there use.