Smallholders with older or second-hand machinery must know how to clean old engines.

South Africa is a dry, dusty country. At the same time, fuel in South Africa, whether diesel or petrol, is often stored in and dispensed from tanks or drums that are less-than-perfectly clean.

As a result, because of all the dust in the air and the dirt in fuel, two of the most important components on any engine ~ be it of a car, bakkie, tractor or lawnmower ~ are its air filter and its fuel filter.

And the filters on tractors, earthmoving equipment, mowers and vehicles that operate predominantly on sand roads and thus are enveloped in clouds of dust for a good part of their working hours, are particularly at risk.

Servicing an air filter on a newer engine is as easy as unscrewing the covering, whipping out the paper-based element and sticking in a new one.

clean old engine
Paper air filter element.

On an older engine, with an oil-bath filter, things are a little more complicated, as there is no paper element to replace. An oil-bath filter comprises a wire mesh filter element the bottom end of which stands in a reservoir of oil. This oil coats the wire of the mesh, providing good adhesion for particles of dust that fly past as the air moves into the engine. In time the captured particles flow downwards into the oil bath, where they remain as a black sludge until the bath is cleaned and refilled.

But here’s something that may seem counter-intuitive. Oil, which one believes will not mix with moisture, is in fact hydroscopic. That is, it does, over time, absorb moisture and it will, in time, turn from its usually transparent golden-brown colour into a milky white fluid. (You can see this most dramatically in the sump oil of an engine that has blown a cylinder head gasket or cracked its block, resulting in cooling water mixing with the oil).

Oil mixed with water loses many of its lubricating qualities, as well as its ability to attract dust particles.

Servicing an oil-bath filter naturally requires cleaning and refilling the reservoir with oil, and washing and drying  the wire mesh element, before reassembly.

At the same time as servicing the air filters, it is always worth checking the integrity of air feeder pipes and their connections for leaks, loose clamps etc.

Like the throw-away paper elements of modern air filters, modern fuel and oil filters also have throw- away components.

On older engines, however, these are often of the serviceable and reusable type. On some engines, the fuel filter comprises nothing more than a sturdy glass reservoir through which the fuel passes on its way from the tank to the engine, the idea being that crud in the fuel, in the form of rust particles, or water, will settle out into the reservoir before the fuel is combusted.

Oil bath air filter.

While this may seem quite a crude hit-or-miss idea it is remarkable how much such a filter will catch over time.

So, before the heavy usage period of summer starts, now is a good time to focus some maintenance attention on the filtration of your engines ~ tractor, car, bakkie or mower.

Main Image: A dirty Vaaljapie filter.

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