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Help Engines Breathe Easier

Farm machines are often surrounded by dust when working in a field, and dust is one thing you don’t want to let into an engine. Dietrich Schellenberg, Marty Zuzens, Peter Lung and Dennis White, instructors at Assiniboine College’s School of Trades and Technology, offer these tips to keep an engine’s air intake system functioning properly.

A poorly maintained intake system restricts the flow of air for combustion, robbing the engine of power. That translates into higher fuel consumption and wasted money. But that’s not all. Allowing dirt into the engine can lead to a catastrophic engine failure. Going over the air intake system carefully, checking pipes, connectors and clamps every time you perform an engine service, can help prevent that.

As part of a good maintenance program, the instructors say pay attention to air filter restriction indicators — if a machine is equipped with them. These indicators may be a gauge in the dash or a small unit near the filter. Modern indicators are usually pretty accurate. Rely on them rather than opening up the air filter housing regularly for an inspection. Frequently removing filters for inspection could be considered over-servicing, which can actually lead to filter or system contamination if you are not extremely careful. The idea is to keep things buttoned up for as long as possible.

Many modern machines have air intake pre-cleaners that work on the Venturi principle, aided by the exhaust system. The Venturi principle is named after an Italian physicist who discovered a volume of air moving through a restriction speeds up.

As air speed increases inside the restriction, an area of low pressure is created — the same principle is used in carburetors to draw fuel into an engine. With pre-cleaners, the low pressure draws dust out of the air flow and blows it out the exhaust before it reaches the filter.

That allows for less-frequent air filter service, particularly on combines that work in excessively dusty conditions. But if your engine has a pre-cleaner collector bowl at the intake instead of blowing dust out the exhaust, it must be emptied whenever there is a layer of dust in it. In very severe conditions, this may have to be done daily.


If it becomes necessary to remove the air filter, inspect it for cleanliness by putting a trouble light inside and looking at how much light passes through the paper element. There should be a nice glow visible. If you see a very bright point of light, the filter has a hole in it, and you should not reuse it.

If the filter is dusty when you take it out of the housing, tap it lightly in your hands to shake off the loose particles. Then, using

an air compressor, reduce the line pressure to no more than 30 psi and carefully blow compressed air from the inside out. Never do this with full air pressure. It will tear the element, rendering the filter useless. Also do not tap the filter too hard. That will dent it, which will also ruin it.

After servicing the filter, inspect it again with a light to make sure you haven’t damaged it and there are still no holes in it. If you remove a filter that is loaded with dirt and chaff, do not bother cleaning it — just replace it.

Some machines have a secondary, smaller air filter inside the larger primary one. If this filter is dirty, never clean it; just replace it. Finding this filter dirty means your primary filter has a hole in it. It too must be replaced.

The secondary filter is considered a safety element. It’s the last line of defence the engine has from sucking in dust and dirt, which is abrasive and can quickly wear down internal bearings.

A secondary filter element should be changed at least every second year. Always replace all gaskets that come with your new filter, too. During servicing if you notice any gaskets that have lost their shape or are damaged in any way, always replace them. Filters and gaskets are much cheaper than engine overhauls.


For an older machine that uses an oil bath air cleaner, it must be serviced with every oil change — or sooner in dusty conditions. Remove the bowl, drain the oil and clean out the sludge. Refill it with the same viscosity oil as in the crankcase.

Scott Garvey specializes in writing about tractors and farm machinery technology for publications in Canada and Great Britain. He’s also a former affiliate member of the Society of Automotive Engineers (SAE). He farms near Moosomin, Sask.

About the author


Scott Garvey

Scott Garvey is a freelance writer and video producer. He is also the former machinery editor at Grainews.



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