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Think about what's happening and you won't want to do it.

There’s a current craze for fitting a plain or oily-foam ‘sock’ over a snorkel. It may seem like a good way of keeping your air cleaner element dust free, but it isn’t.

What’s the point of fitting a snorkel to a 4WD, bearing in mind that the original ‘snorkel’ was a way for a submarine to ‘breathe’ while underwater?

In the case of a snorkel on a 4WD the purpose is to elevate the engine air intake, so that a 4WD can drive through a water crossing without risking water entry into the engine. A side benefit is that this raised intake may breathe air with less dust in it than an air intake closer to the road.

Another possible benefit of a snorkel with a forward-facing ‘scoop’ is a ‘ram-air’ effect, pressuring the intake air to help reduce pumping losses in the engine. This is less relevant in the case of a turbocharged engine, where the turbo provides much more ram effect than any scoop possibly could.

Some snorkels are fitted with a ‘cyclonic cap’ pre-cleaner and the most common is the one fitted to LandCruiser 70-Series factory snorkels. This circular device creates ‘swirl’ in the incoming air and the centrifugal force of this swirling air flings large dust particles to the outside of the cyclone device, where they can be ejected manually, or automatically.

An important part of the pre-cleaner design is that it doesn’t create any obstruction to the incoming air, even if the collection chamber is full.

Some enthusiasts and after-market people have theorised that if a pre-cleaner is desirable to keep excess dust out of the main air cleaner element, why not use a screen of some sort on a plain, non pre-cleaning snorkel scoop?  They opted for ‘socks’ made of simple cloth, or foam plastic soaked with sticky oil, to act as dust-screening pre-cleaners.

The one major problem with this ‘solution’ is that these socks clog up with dust that restricts airflow into the engine. This ‘strangling’ effect on air flow into any engine can cause a loss of power and excessive fuel use. In the case of a turbocharged engine it’s also likely to cause turbo overheating. Restricted air flow can confuse the engine’s ECU and cause other combustion-zone problems.

Another quite nasty and dangerous situation can occur if the sock is rinsed clean with petrol; we’ve already heard of an engine ‘runaway’ when petrol fumes sent the engine revs soaring!

Don’t fit a sock!

The best way of keeping dust out of your air cleaner element is by not driving in other vehicles’ dust clouds. If you’re in a convoy, drop back out of the dust and maintain contact by CB radio.

If you can’t avoid prolonged driving through clouds of dust, fit a proper cyclonic-type pre-cleaner.