Keeping an eye on filters is essential

VITAL: Clean air, oil and filter can ensure the longevity of your vehicle' engine. Cicra 2009. Pic. Unknown.
VITAL: Clean air, oil and filter can ensure the longevity of your vehicle' engine. Cicra 2009. Pic. Unknown.

Nothing is more important for the health and longevity of an engine than ensuring that the fuel supplied to it, the air it inhales for combustion, and the oil circulating though it are clean.

Nothing is more important for the health and longevity of an engine than ensuring that the fuel supplied to it, the air it inhales for combustion, and the oil circulating though it are clean.

That is why air filters, oil filters and fuel filters are such vital components.

Keeping an eye on these items and replacing them when necessary are jobs that any home mechanic can do, even on modern, fuel-injected engines. Not only will this save you a lot of money, but you will also be certain that the job is done right. Let us briefly look at the different filters found on a car.

Air filters used to be of the oil-bath design in which the inrushing air is first directed downward towards a pool of oil where it has to make a sharp U-turn to find its way upward through a housing filled with wire or fibre mesh in almost touching contact with the oil at the bottom.

Particles of dust and grit which are not thrown downward into the pool of oil at the U-turn, are captured by the oil-wetted mesh on the upward path. A clever design, which worked extremely well, as many older drivers can testify when they recall the billowing, choking dust of dirt roads.

Even today, oil-bath air cleaners are used on some off-road equipment because they are unrivalled in their ability to filter out a great deal of dirt without loss of filtration efficiency or airflow.

But cleaning out an oil-bath air cleaner was messy for an owner who didn't like to get his hands dirty, and furthermore the air coming out of such a filter has a trace of oil mist in it which is a no-no for emission controls.

So, in the early 1960s oil-bath air cleaners made way for the paper-element filters used almost universally on modern vehicles. Most fuel-injected engines use a pleated paper filter element in the shape of a flat panel, placed inside a plastic box which is connected to the throttle body by an intake tube.

Carburettor engines typically use a cylindrical air filter situated above the carburettor. The term "paper element" is somewhat misleading, because the material from which the element is made bears only a superficial resemblance to paper used for writing or packaging.

The material offers little restriction to airflow when new, and the filtration efficiency will in fact increase as the pores in the material become partially blocked by captured dust and grit. However, the element has to be replaced before the blockage restricts airflow significantly.

This is critical for diesel engines, which need to inhale about 20percent excess air to keep combustion chamber temperatures down. A blocked air filter, whether clogged by dust or soaked with water, poses a danger to a diesel engine.

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