The Gear You Need for Water Crossings in your 4x4

Nov 04, 2023

WHETHER YOU’RE four-wheel driving in the Top End, the High Country or even in Central Australia, chances are you’ll eventually encounter a body of water that will need to be crossed if you want to continue with your journey.

There are many rules before attempting a water crossing, such as checking the depth and the flow of the water, looking for hidden obstacles and planning your exit point, but in this feature, we’ll focus on what gear you’ll need to prepare your vehicle so it can make it to the other side.

You’re not going to make it across any body of water if you’re engine isn't running, so the first bit of gear you need to consider fitting to your 4×4 is a snorkel. If your 4×4's engine ingests water, the best-case scenario is it will stall, leaving you stranded in the middle of the water crossing. The worst-case scenario is your engine will suffer hydraulic lock (when the pistons try to compress non-compressible water), which can cause extensive and expensive mechanical damage, leaving you not only stranded but also with a potentially expensive tow back into town.

Most standard four-wheel drives have an air intake for the engine at around headlight height. Some of these simply have an opening above or behind the headlight while others will have a pipe leading through the inner guard. The air intake leads to the air filter box and then to the engine. Regardless of the location of the air intake, headlight height is simply not high enough for many water-crossing situations.

Your vehicle will have a stated maximum wading depth. In the case of the Volkswagen Amarok it's just 500mm, while a Ford Everest has a claimed maximum wading depth of 800mm, and Land Rover claims a class-leading 900mm for the Discovery 5. The problem with manufacturers’ stated wading depths, however, is that there's no guarantee the engine still won't suck in a gob full of water, because the forward momentum of the vehicle will create a bow wave that is higher than the still body of water it's driving through. Driving slowly is one way to minimise the height of this bow wave, but this is not always possible – if the ground beneath the water is boggy and slippery, for example, you’ll need a fair bit of momentum to ensure you don't get stuck.

The best way to stop your engine from ingesting water is to fit a raised air intake in the form of a good quality snorkel, with good quality fittings. A well-designed snorkel will attach to one of your vehicle's A-pillars so the engine will source air at roof height, which is much higher than the depth of any body of water you should ever attempt to cross. The snorkel will also attach to the vehicle's outer front guard and have plumbing that feeds through said guard to the air filter box.

It should be noted that not all snorkels are created equal. A good-quality snorkel will have airtight fittings so that no water can be sucked into the engine. It will also be manufactured form UV stable material that won't fade or crack under the Aussie sun, and it will be designed in such a way that it won't restrict airflow to the engine, which can reduce performance and affect fuel economy. Always go for a known brand when fitting a snorkel; some cheaper snorkels will leak, fade and crack, and can also produce annoying induction noises due to poor and untested designs.

Manufacturers and distributors of snorkels include Safari 4×4 Engineering (R-Spec, V-Spec and ARMAX), TJM Products (Airtec), Ironman 4×4, Ateco (Airflow) and Sherpa 4×4.

Even on shallow water crossings, chances are your 4×4's differentials are going to cop a dunking and, like your engine, they too can ingest water.

As a vehicle's diffs heat up when driving, pressure builds up inside them, so they are equipped with a one-way valve (breather) that allows pressure to be alleviated. As the diffs cool, which will occur when the diffs are plunged into icy cold water, for example, the pressure inside the diffs will be reduced, creating a vacuum, so they will want to suck in water. The one-way valve is designed to prevent this, but is not always effective. Even if the valve proves watertight, the vacuum inside the diff can result in water being sucked in through other points, such as the axle oil seals.

The best way to prevent the diffs from sucking in water is by equalising the pressure inside and outside the diffs by removing the one-way valves and replacing them with diff-breather extension tubes. The open ends of the tubes will be affixed to the vehicle's firewall or somewhere else high up in the engine bay where they won't be submerged in a water-crossing situation. They will also be fitted a special filter that lets air in and out but prevents water ingress.

Your vehicle's gearbox and transfer case are also susceptible to water ingress due to variations in pressure, and they too will be fitted with one-way valves that can be replaced by pressure equalising breather extensions tubes and filters.

Several four-wheel drive specialists make diff breather extension kits to suit a wide range of four-wheel drives, including Piranha Offroad, ARB, Ironman 4×4, Opposite Lock and Harrop Engineering. The Harrop design has four ports – for front and rear diffs, gearbox and transfer case – and an equaliser hose that can be mounted inside the air box or up near the snorkel intake, so no filter is fitted at the inlet point.

A water-crossing bra is designed to keep water out of your vehicle's engine bay, which is important for several reasons.

If you don't have a snorkel fitted to your vehicle, a water-crossing bra is a must, as it may help prevent water from entering the vehicle's induction system via the air intake. But even if you have a snorkel fitted, attaching a water-crossing bra to your vehicle is still well worth the effort, especially for deep crossings.

As well as the engine, there are plenty of other components under your 4×4's bonnet that don't like water, such as the ECU, alternator, fuse boxes, batteries, wiring and other electrical bits and pieces. A water-crossing bra will divert water around the front of the vehicle rather than letting it through into the engine bay, where it can cause havoc after being sprayed around by the vehicle's cooling fan.

The fan itself can also be damaged by water, as can the vehicle's radiator. Most cooling fans are made form nylon or some other plastic, and when water passes through them the blades can bend forwards and cut into the radiator, causing a complete loss of coolant. A water-crossing bra will prevent this from happening.

Prior to the advent of dedicated water crossing bras, four-wheel drivers would make do with a tarp attached to the front of the vehicle with rope. While sometimes successful, if the tarp was not properly secured it could come loose and detach from the vehicle altogether or foul up underneath the vehicle. Modern water-crossing bras are designed for a better fit to the front of vehicles and are far less likely to come loose, or cause damage to vehicle paint. The MSA 4×4 design, for example, incorporates straps and shock cords for fast, easy and secure fitment., while the ARB Crossing Cover also has clear headlight panels, a recovery strap pocket and under-vehicle mesh panels to allow water out when exiting a crossing.

Of course, a water-crossing bra will only perform as intended if the vehicle has forward momentum; if you stop in the middle of a crossing it won't keep water out of the engine bay.

Other things to check on your vehicle before diving into a water crossing include door seals and tailgate seal. The last thing you want is water getting in to the cabin of your vehicle, where it can ruin carpet and damage any valuables that might be on the floor, or into the tub of your ute where food and other not-so-waterproof stuff might be stored.

You should keep your window down when tackling water crossings in case you need to exit the vehicle in a hurry. Make sure you have an emergency seat-belt cutter/window breaker within easy reach.

Always carry a can of WD-40 or other water-displacement product in your vehicle. Before making a crossing, spray WD-40 over electrical connections, both in your engine bay and on your winch (if fitted).

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