Driving tips for a 4×4 through water crossings
Water crossings can provide some of the most exhilarating and challenging 4X4 Driving around. They can also prove to be the most expensive!
A 4×4 is not an amphibious vehicle; in fact they are not even waterproof. The actual depth that you can cross depends on your vehicle. For example, a stock Toyota Land Cruiser may be submerged at the depth a raised Land Rover doesn’t even wet the doorsills.
As a general rule, if it’s above the top of your wheels it’s probably too deep. A water crossing should not be attempted by inexperienced or ill-prepared 4×4 drivers.
Prior to a water crossing, it is a good idea to place your recovery gear on top of other luggage. The last thing you want to do is be searching under your cooler, tents and baggage for your recovery gear when you are stuck in the middle of a croc infested water crossing.
Vehicle Preparation
The first thing to do before any unfamiliar water crossing is to walk it. If you cannot walk it you cannot cross it. If the water is flowing too quickly to safely walk the crossing, then it cannot be driven across. Remember, vehicles actually float until water seeps into them. When you walk the crossing you are actually starting your vehicle preparation. You are giving the axles, diff’s and gearbox time to cool down while you find out exactly how deep the water is.
Diff Breathers
When a hot axle hits cold water it cools rapidly. This has the effect of lowering the air pressure inside the axle and the diff housing, causing air to be drawn in via the diff breathers. Extending your diff breathers higher up the chassis (standard on most Land Rovers) with the aid of plastic tubing is a “must do” for regular water goers. However, it is no guarantee that water will not enter your diff. The sudden reduction in air pressure inside your diff can still cause water to be drawn in via your axle seals if the diff breathers do not equalize the pressure quick enough. This is why it’s still necessary to allow the vehicle time to cool down, even when extended diff breathers are fitted.
Air Intake
Water and engines do not mix very well, and when they do it almost always results in bent pistons, valves and crankshaft commonly called “hydro-locking“. If you think this sounds expensive your right. The positioning of the air intake is critical to how well a vehicle can handle a crossing. For example certain Land Rover models have their air intake directly behind the headlight, which is great to allow cold air into the engine but unfortunately is equally as great in directing water into the engine.
NEVER attempt a water crossing where the water depth is above the air intake height. If you intend doing regular water crossings, it’s a good idea to fit a snorkel as it raises the air intake to your roofline. It doesn’t mean you can use your 4WD as a submarine!
Engine Bay Protection
Placing a tarpaulin across the front of the vehicle minimizes water entering the engine bay by creating a bow wave, provided forward momentum is maintained. The result is less water for the radiator fan to spray over the ignition system, less chance of water entering the air intake and less likely for the fan to propel its way up to and through the radiator.
Diesel vehicles are usually better for water crossings as you do not have the ignition system to worry about. Water in the ignition system usually results in a stalled engine and not actual engine damage, though this is of little comfort when you find yourself stuck in the middle of a crossing. Depending on the water depth, it’s advisable to climb out of your window rather than open the door and flood your carpets. To minimize stalling from a wet ignition, it’s a good idea to spray all the ignition system with water repellent beforehand.
Radiator Fan
While under the hood spraying water repellent, check to see what type of radiator fan is fitted. Most 4WD’s these days have the viscous coupling type, which means that when the engine is cool enough the fan doesn’t spin at full speed. With the engine off, try and turn the fan. If it turns easily, you will probably get away without having to take off the fan belt. If it doesn’t turn easily or yours is the fixed type, then you should remove the fan belt, If you don’t and water enters the engine bay, the fan may act as a propeller, bend forward and cut a nice round hole through your radiator. It’s certainly one problem you don’t want to discover once you have completed the crossing. Even if it doesn’t affect your radiator, you still do not want water being sprayed around, especially in a petrol vehicle.
Walking the Crossing
When walking your water crossings its best to walk in the intended wheel tracks to find if there are any hidden rocks or potholes, as well as for checking the depth. Potholes at common crossings are often caused by previous vehicles spinning their wheels after hitting a submerged rock. So if you find a pothole, check for submerged rocks. It’s a good idea to place markers at these points so you can avoid them. It’s been known for a vehicle attempting a relatively easy crossing to suck in water when a single pothole has caused the hood to momentarily dip below the water level, causing water to enter the air intake, resulting in hydro-lock and a damaged engine.
