by Skip

Water crossings can be both a very satisfying, exciting part of 4WD'ing, but also a very hazardous, expensive and even dangerous pastime. Whether you are crossing water because there is no other way to your destination, or just for fun, you should take note of the following tips.

The first thing to do when approaching a water crossing is to stop, get out of your car, and assess the crossing. Just "looking" at the water is not a good way to determine it's depth. It is best to walk through the water to gauge it's depth, and also to check for any submerged obstacles, such as rocks, logs, or deep holes. If there are obstacles, then you need to plan your route through the water to avoid them, which may also involve getting some volunteers to stand at various way-points across the water to guide you safely through. Also assess how firm the bottom is, to determine if you may have any traction problems (for example, if the bottom is soft sand, then it may be wise to lower your tyre pressure). If the water is flowing, you need to assess the risk of you 4WD being swept down stream, which could be disastrous (as in the picture above). If the water is flowing and is over bumper height, then a "wave" can build up against the side of the vehicle, pushing it sideways. One last warning - if it is likely that crocodiles may inhabit the area, it could be dangerous to walk through the water, so it might be wise to seek some advice from local folks.

It is essential to prepare your 4WD for the crossing, especially if the water is deeper than bumper height. Most common problems encountered during water crossings are caused by the engine's cooling fan entering the water. This can cause water to be sprayed all over your engine, causing petrol engine's ignition systems to stop working. In more severe cases, the fan blades can bend forward (as they are not designed to move water) and destroy the radiator. The way to avoid these problems is to remove the fan belt, or adjust it so that it has very little tension, to allow the belt to slip. Most engines can run for a short time without the water pump and alternator connected. Most modern 4WDs have viscous couplings on the fan, which allows the fan to free spin when the engine or surrounding air temperature is low, which can also be sufficient to handle a moderate amount of water (you can usually hear when the viscous coupling engages on most cars). Leaving you car to cool down for a while before the crossing can also help the coupling to dis-engage, and also lets the front and rear diffs cool, so that they are less likely to "suck in" water through their breather pipes, when then suddenly get dunked in cold water.

The next thing to do to prepare your vehicle is to fasten a tarpaulin over the front of you 4WD. This helps to minimise the amount of water entering the engine compartment, and also helps to create the "bow wave" as you cross the water. Remember to tie the tarpaulin on firmly, as water places quite a bit of pressure on the tarp. If the water is deeper than say headlight height, then a wise precaution is to fit a snorkel to the air intake, to prevent the 4WD from ingesting water. Generally speaking, if your engine gets a "mouthful" of water, you will seize it, which is very inconvenient and expensive. Another precaution that may be necessary, is to place an extension on the exhaust pipe, to prevent water from being forced into the exhaust system, which can make a motor idle low, or even stall. On deeper or longer crossings, you may also take further precautions, like extending the height of the diff breathers, fitting plugs to the clutch housing and other breathers, checking and cleaning all door seals etc. Remember - 4WD's do float! The deeper the water, the more buoyancy your car has, so the less traction you will have with the bottom.

Make sure that your recovery gear is on hand, in-case you get stuck, so that you can be pulled out before the water begins to seep in through your door seels! In flowing with a loose bottom, it is important to have your vehicle recovered quickly, in case it begins to sink, as the water removes the dirt from around your tyres. If the river is tidal, you also need to be aware that the tide could come in, and that salt water is particularly damaging to vehicles. If you have a winch, take note of suitable winch points (trees etc).

When entering the water, keep your speed down, to somewhere in the 5 to 10Kph range, which usually equates to 1st or 2nd gear, low ratio. Going too fast will cause water to go everywhere, including in your engine bay. Too slow may not provide you with enough momentum if you encounter a soft spot. The speed needs to be just right to maintain a good "bow wave" which provides a lower water level for the rest of the car. Avoid changing gears (or stopping), as use of the clutch could cause water to come between the clutch plates, resulting in severe clutch slippage, and possible loss of all drive! Do not over rev the engine, as you risk damaging fan or radiator (you may also overheat the engine if the fan belt is removed). Do not under rev the engine, as it may stall, due to water settling on electrical parts (petrol engines) or water entering the exhaust pipe. Use maybe 2000 to 2500rpm (or perhaps a bit lower for diesels). If you have to climb a bank on the other side of the water crossing, begin applying power just before the bank.

Now that you have successfully negotiated the water crossing, you can signal for any other vehicles to come across - only ever have 1 car in the water at a time, so that there is always a recovery vehicle, and so to avoid having to stop if the car in front stops. Now you can de-rig you car - re-connect fan belts, take off tarps etc. Remember that your brakes may not work very well whilst wet or muddy. If there is any mud stuck to your wheels, then clean it off, so that brakes and wheel balance are not effected. You should also have your diff, gearbox and transfer case oils checked for signs of water contamination at your earliest convenience, as water can cause these major components to fail, if not detected soon enough.             (c) 4WD Encounter 1998

 These pages were last updated on 25th July 1999.
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