The West

4WD: Avoid a watery grave
Water crossing:  Tackling deeper crossings without a snorkel to stop water ingress into the engine can be critical for a petrol engine but fatal for a diesel. Picture: Craig Perry

Sooner or later, you'll be out in your four-wheel-drive and encounter something considerably bigger than a puddle.

Improve your 4WD skills:

With the potential to suck water into your engine or drift away downstream, a water crossing requires care to avoid an engine rebuild or endangering you and your passengers.

Your vehicle manual will specify the maximum wading depth for your particular 4WD, unless modifications are made.

If you're planning a big trip or water crossings are common at your preferred off-road destinations, then take additional steps to safeguard your car's engine and driveline.

Most importantly, fit a snorkel to raise the air intake for your engine above bonnet height.

Second, extend the height of the diff breathers and remember to wait before entering the water to allow your driveline to cool down.

Plunging a hot diff into cold water will create negative pressure that sucks the water into the diff, rapidly destroying bearings. Carry a water-crossing blind to deflect water and help create a bow wave, pushing water around the vehicle away from the radiator grille.

Purpose-designed blinds that can be secured to barwork but allow easy winching access are more effective and faster to fit than the simple blue poly tarp.

The safest option (unless the crossing is likely to be croc-infested) is to walk through the water first.

This allows you to assess how fast the water is flowing and the firmness of the river base, as well as identify large holes or fallaways.

If the water is particularly uninviting, use a stick or shovel handle to probe as far out from the bank as possible. Watch the water closely while your diff cools to assess likely speed and possible obstacles.

As a general guideline, choose second gear, low range. Don't charge in too fast because you could send a burst of water straight into the engine bay.

The standard rule applies - don't attempt to change gears part way through the obstacle as you don't want to lose momentum and start slip-sliding downstream.

Where appropriate, cross the water diagonally, with your exit point slightly further downstream than your entry.

This allows your vehicle to work with the current rather than fighting across it - the same as a swimmer crossing a rip.

Having a second vehicle standing by to assist is particularly important where there is a risk of rapidly sinking, such as a freshwater stream crossing a sandy beach.

From an environmental perspective, pause slightly as you exit the crossing, assuming it is safe to do so.

This allows water to drain back into the stream, reducing bank erosion and muddying of the water downstream. Having successfully negotiated the crossing, apply your brakes a few times as you drive off to speed up the removal of water from the brake linings.

Once you get home and have cleaned off the mud, don't forget to check the fluid in your vehicle's diff and transmission to ensure there's no contamination that could lead to expensive repairs if not promptly removed.

The West Australian

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