Water Crossings
Water crossings can provide some of the most exhilarating and challenging
4WDriving around. They can also prove to be the most expensive!
A 4WD 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 Subaru may be submerged at the depth a raised Hilux doesn't even wet the doorsills.
As a general rule, if its above the top of your wheels its probably too deep. A water crossing should not be attempted by inexperienced or ill-prepared 4WDrivers.
Prior to a watercrossing, 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 eskies, tents and suitcases for your recovery gear when you are stuck in the middle of a crossing.
Vehicle Preparation
The first thing to do before any 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, diffs 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
Landcruisers and Patrols) 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 equalise the pressure quick enough. This is
why its 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. 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 Toyota Hilux 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 (An easy fix for this is to remove the plastic tubing from
the air cleaner to the headlight when crossing water).
NEVER attempt a water crossing where the water depth is above the air intake height. If you intend doing regular water crossings, its 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 tarp across the front of the vehicle minimises 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 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, its advisable to climb out of your window rather than open the door and flood your carpets. To minimise 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 bonnet 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. 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 are
often caused by previous vehicles spinning their wheels when they grind to a half 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 con avoid them. Its been known for a
vehicle attempting a relatively easy crossing to come unstuck when a single pothole has
caused the bonnet to momentarily dip below the water level, causing water to enter the air
intake and resulting in a damaged engine.
Driving Technique
With a mental picture of your route, or better still, with markers in place, and all your
vehicle preparation done, its time to start the crossing. Before you enter the water,
remember to take off your seat belt and wind down your window.
Using low range second gear at 1500-2000 rpm (for most vehicles) creates just the right bow wave. Its important to get the speed just right as too fast will send water everywhere while too slow may flood the engine bay. Hopefully you follow your markers and get to the other side with no problems. But if you do strike problems avoid using the clutch as this may allow water to get between the friction plate and the flywheel, resulting in limited drive.
If the wheels start to slip, its important not to over-rev the engine but back-off the accelerator and hope the wheels regain traction. Excessive wheel-spin will not help.
If the engine stalls, put the vehicle in neutral without using the clutch and attempt to restart. If luck is on your side the engine will fire up. Now is not a good time to wish you had already disconnected the fan belt, as your engine bay will be flooded. Its normally best to use 1st gear low range and with a minimum of clutch usage, try and extricate yourself from this predicament.
Maintenance after
Water-crossings
So once you have successfully crossed to the other side and are on your way home, you
don't need to give the water crossing a second thought, right? Wrong! Any crossing at axle
depth or deeper necessitates a checking of the diff oil for water contamination. Having an
extended diff breather is not a 100% guarantee of waterproofness and any crossing above
your axles without extended diff breathers should mean a mandatory inspection.
Checking your diffs for water contamination is very easy. Since water is heavier than oil, it will collect at the lowest point in the diff, right where the drain plug is located. After allowing time for your vehicle to cool, just loosen the drain bolt and run a small amount (~20mls) of the diff oil into a glass. If you're unlucky enough to have water present, the diff oil should be drained. It is best to flush the diff several times to ensure all traces of water are removed. Milky coloured oil also indicates water is present and should also be changed.
If you're like the majority of 4WDrivers, you won't be able to change the diff oil until you get home, because you won't have spare oil and a sump pump to change it. If you suspect contaminated oil (a deep water crossing without extended diff breathers or perhaps you have leaking diff seals) then you can try and remove the water by draining the diff until only oil comes out the drain hole. Do not drain too much and leave your diff short of lubrication. Collect this oil and water emulsion as you should never dispose of oil into the environment. Save it till you get back home and dispose of it properly.
Its not only diffs than con have water contamination, but also your gearbox, transfer case and engine oil. However, it is usually only when a vehicle is stationary in deep water that these components are contaminated.
Amongst other items to check are bar mounted electric winches. These components may not be used for extended periods and when they're needed you may find they have seized up. If the winch has been submerged in water it is advisable to strip it and grease it accordingly. A quick operation of it after a crossing may prove it still works, but you may find out when it seizes that you washed all the grease out 6 months ago!
A water crossing is something that should not be taken too lightly as it has the potential to do expensive engine and drive-train damage. However, with the right vehicle preparation and post crossing maintenance, you can enjoy some of the most challenging 4WDriving around.
Watercrossing Summary
Vehicle Preparation
Driving Technique
Post Watercrossing maintenance
These pages were last
updated on 22nd Oct 2004.
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