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Trail Savvy: Water crossings


River crossings are an inevitable challenge. Handled correctly, they can be made without incident, but they can also go wrong fast.

Avoid deep crossings if possible, and always approach them with respect. We’ve had our fair share of mishaps − from a blown engine in a V10 Touareg, to a partially submerged Land Rover pulled out by a three-wheeled digger.

Step 1 – Assess the situation

By ‘assess’, we mean make sure that you won’t drown your vehicle or get washed downstream. A very rough rule of thumb is that standard 4x4s shouldn’t ford deeper than tyre height, because many manufacturers locate the air intake at the top of the wheel arch.

You can wade deeper than this without a snorkel by creating a bow wave in front of the vehicle; keep to a steady speed just above walking pace (about 10km/h) in second gear low range.

Know your vehicle’s wading depth, but also approach every situation with due caution. Look for the shallowest point, signalled by current flows, and watch where animals or the local people are crossing. If the water is flowing too quickly to walk through, then it’s also too strong to drive through. Always try to walk a deep crossing before driving it, to check for depth, rocks, holes and traction.

Step 2 – Get your vehicle ready

In places like the Okavango, where crocs and hippos are a real underwater threat, scouting a crossing on foot is not wise. In that case, attach a long tow-strap to a rear recovery point, and link it to another vehicle in the convoy. If you get stuck, the vehicle you’re connected to can simply pull you out without anyone getting wet.

If you do get stuck, but have an escape plan, keep the engine running – this prevents water from entering the engine via the exhaust.

Before reaching the water, make sure that all breather hoses are connected. A missing or loose breather hose on the differentials, transfer case or gearbox will cause water to be sucked in, as hot components contract in cold water. Also make sure any wading plugs on the bell housing are secure and sealed.

In older petrol engines, distributor caps can be sealed with Q20 or a similar silicone-type spray, and on all cars, the battery terminals should be sealed with grease or Vaseline.

Radiators and fans are susceptible, especially when a ‘windgat’ driver enters the water too quickly. This can push the blades of a fast-spinning fan back into the radiator, breaking the blades and damaging the cooling fins. Go slowly, to avoid this. If momentum is going to be required, disconnect an electric fan (remove the wiring or fuse), or jam a viscous fan with a rag. A waterproof sheet fixed to the grille area in front of the radiator will also break the force of the water hitting sensitive components.

If your vehicle has a properly sealed snorkel, you can theoretically drive deeper, but will risk flooding the cabin and drowning the engine’s ECU – which will end your trip. Remember that snorkels are mainly to keep out dust, and have water drain holes. On a recent deep crossing in Botswana, a lot of water burst through the aircon vents, causing a nasty smell when it stagnated inside the system. Best to put your aircon on recirculate to prevent water ingress. If you drive a Defender, you’re going to get wet anyway.

Step 3 – The approach

In 4×4 driver-training, you are taught to remove your seatbelt and open the windows – this makes it easier to escape if you roll over or become submerged in a hole. This may be impractical if the water is very deep, as water will flow in; but rather be safe than let the worst happen.

If the crossing has a clear exit, it’s usually best to aim straight for it. Other vehicles will have used the same route and created an underwater track. If you do get stuck, do not spin your tyres, as you dig holes very quickly under water. Rather try to reverse along your own tracks. Failing this, you’ll need to recover the vehicle, keeping it idling at all times.

As tempting as it is to make a massive splash… don’t. Put the vehicle in second gear low-range and enter slowly, accelerating to create a wake around the tyres. Try not to stop, but if you stall, it’s best to have your vehicle pulled out without attempting a restart as water may have entered the engine.

Step 4 – After crossing

You’ve made it through. What now? If you’ve done lots of crossings, check that your oil is black. Creamy oil means that there’s water in it, and you should drain and refill with good oil as soon as possible. Also be sure to regularly grease all the manufacturer’s recommended points.