As an opening statement it should be said that a water crossing should not be attempted by the
inexperienced, especially deep water crossings. A water crossing can be
fatal to an engine and even worse, to occupants of the vehicle in the worst case
scenario. Never underestimate the force of flowing water. Water
weighs about 62.4 pounds per cubic foot and typically flows downstream at
approximately 6 to 12 miles an hour. For each foot the water against a
vehicle, 500 pounds of lateral force are applied to the vehicle. As a
vehicle enters water, 1500 pounds of buoyant force are produced for each foot
that the vehicle is submerged. This basically means that a vehicle weighs
1,500 pounds less for each foot of water. When the buoyant force exceeds
the weight of the vehicle, it begins to float and is now at the mercy of the
water as the flowing force of the water is exerted on the vehicle, pushing it
downstream. For typical cars, this translates into a floating car in just
two feet of water. To put it into a 4x4 perspective, a 4x4 vehicle is
typically lifted to some degree. This puts the buoyant part of the vehicle,
mainly the body although tires are quite buoyant, higher than cars, but in many
cases not by much. The key point is that like a boat, the water displaced
creates the buoyancy and vehicles actually float until water seeps into them.
But by the time water seeps in, it may be too late.
That being said, a water crossings in a 4x4 can sometimes be some of the most
exciting and challenging situations you do when offroad. Water crossings
can also become some of the most expensive.
A 4x4 is not an amphibious vehicle, nor is it waterproof.
Even those 4x4 vehicles that have been modified to tread water have their
limitations when crossing through deeper waters. The depth to which a vehicle
can be submerged depends greatly on the vehicle itself. Those factors not
only apply to the vehicle but the age of the vehicle as seals deteriorate. As a rule of thumb,
the depth limit of a vehicle is about the top of the tires and even that is probably too deep.
As a rule of thumb, it's a good idea to have your recover
equipment easily accessible and ready for use. When you need your recovery
equipment it may be in an emergency situation where time is critical. If
your recovery equipment is buried beneath other gear, the last thing you want to
do is have to hunt for it especially if you are stuck in a stalled vehicle in
the middle of a river crossing.
Prior to a crossing unfamiliar water is to walk it.
Yes, get wet. If you cannot walk it you cannot cross it with your vehicle.
If the water is flowing too quickly or is too deep to safely walk the crossing,
then it cannot be driven across without serious risk.
Axles, manual transmissions and transfercases typically have
breathers. Breathers are designed to allow air pressure to equalize
between the atmosphere and the inside of the mechanical component. During
use, axles, transmissions and transfercases heat up. When a hot axle or
gear box hits cold water it rapidly cools. This causes the air pressure
inside the axle tube, differential housing, and gearboxes to reduce as the air
molecules to contract. This in turn causes air to be drawn in via the diff
breathers. If your breathers are below the water level or getting
splashed, water will also be sucked into the breathers. Extending your low
lying breathers, especially differential breathers, up higher into the chassis
area using flexible tubing will allow a cooling component to draw dry air rather
than water during a water crossing. This is a necessary modification for
4x4's that frequently encounter water crossings. Of course even with
breather extensions, there is no guarantee that water will not enter your
gearbox and differentials. Rapid temperature reduction, worn seals, loose
bolts, all can be the cause of water getting into places it shouldn't be.
As a preventative measure and the very least giving the axles, differentials, gearbox
and transfercase time to cool down means there won't be as sudden a pressure
drop in these mechanical components causing water to be sucked in.
Engines breath air. As air is pulled into the engine,
it is compressed by the pistons. Water does not compress. If water
gets sucked into your air intake on the engine, it can result in serious damage.
The engine attempts to compress what is in the cylinder and if enough water
enters a cylinder, even a smaller amount of water, the engine can instantly stop
as it tries to compress what can not be compressed, which results in something
called commonly called "hydro-locking". This usually results in bent
or broken pistons, valves and crankshaft. An expensive end to your day.
So where is your air intake? Is it behind the grill?
Behind the headlight? On top of the engine or high atop the vehicle
relocated by a snorkel? The location of your air intake is critical to how well a
vehicle can handle a crossing as far as the air intake goes. Many vehicles
have their air intakes in optimal locations to allow cold air into the engine
such as directly behind the headlight, or through the fender wall.
Unfortunately these locations are great places for directing water into the
engine. Examine your air intake to see where it is pulling air from.
If it is right out there where a head of water will funnel right into the air
intake during a water crossing, you may want to consider relocating it or at the
very least consider a way to temporarily and quickly modify the intake to
prevent damage during a water crossing.
NEVER attempt a water crossing where the water
depth is above the height of your air intake. Vehicles that regularly
encounter water crossings, should consider a more permanent relocation of the
air intake such as a snorkel to raise the air intake. As an obvious word
of caution, do not consider the location of the air intake to be the depth that
you can submerge your vehicle!
The Engine Bay
Aside from submerging your vehicle to the point where it
floats, your engine bay is the primary concern when driving through water.
Almost as important as the air intake is your ignition system. In many
cases a wet ignition system will cause the engine to stall. Not a good
thing in the middle of a river. Water on spark plug wires (especially old,
worn out wires), an old seal on the distributor cap (or no seal at all), a wet
coil or wet ignition module can all cause an engine to stall. Typically
though water in the ignition system usually results in just a stalled engine and
not actual engine damage. But when it does occur, it's usually in a place
where you cannot easily dry off your ignition system components such as in the
middle of a crossing. So protecting the important components from water can be
the difference between getting across and going into recover mode.
When you move through water, the front of the vehicle creates
a bow wave. This raises the water level at the front of the vehicle, the
primary point of water entry into the engine bay. For that reason, go
slow, don't plow through the water as fast you can to get to the other side.
As a preventative measure, some people place a tarp across the front of
the vehicle to minimize water entering the engine bay so long as you keep moving
forward. The result of the tarp method is less water for the radiator fan to spray
over the ignition system and less of a chance for the fan to warp and slice into
the radiator. It also helps to reduce the chances of water entering the
air intake. To minimize stalling from a wet ignition, inspect seals,
wires, and all other ignition system parts and replace worn out parts and seals.
It’s also a good idea to spray all ignition system parts with water repellent
before they get wet. Diesel engines usually do better with water
crossings since they do not have the ignition system to worry about.
The Radiator Fan
Inspect your radiator fan. Take note of type of radiator fan
you have. Most 4x4's have a viscous coupling type fan, also called a clutch
style fan. These fans do not spin at full speed when the
engine is cool and can be a benefit when encountering a water crossing.
You may also find that you have a fixed type fan that always spins at the speed
of the engine. To check your fan turn off the engine and try spinning the
fan. If the fan turn easily with the engine off and there appears to be a
clutch mechanism at the center of the fan this is most likely a clutch type fan you will probably
can get away without taking off
the fan belt. If the fan doesn't turn easy or it is definitely the fixed type
fan, then you should consider removing
the fan belt before entering a water crossing. The reason is when a fan
encounters water, it acts much the same way as a propeller and a light-weight
radiator fan will flex opposite the direction that it blows air, which is
towards the radiator. With most engines having little clearance between the
radiator and radiator fan, this means you may see contact as the fan bends,
possibly slicing into and damaging your radiator.
Walking the Crossing
When you encounter an unfamiliar water crossing and there is
no way to easily examine the depth, sometimes the best way to scout out your
crossing is to get wet and walk it. Walking a water crossing is the best
way to find a good track for your wheels to follow and locate any hidden
potholes and large rocks as well as checking the depth of the water. Since
water has a way of distorting the view of the bottom and making it hard to
estimate the depth it's a good idea to walk in the line that you intend to take,
making note of the wheel tracks and objects between the wheel tracks. Some
people place markers in the water to mark hidden objects or drop-offs or deeper
holes. A marker could be a tall stick or even a tethered balloon.
Techniques for Driving through the
Before beginning the water crossing mentally picture your
route. It's a good idea to take off your seat belt and wind down your window.
When entering the water typically using low range second gear at about 1500-2000 rpm creates just
about the right bow wave. This bow wave of water helps to maintain
momentum and push water ahead of your engine bay. Get the speed just right
is tricky. Do not attempt to drive too fast through the water. The
idea is not to get across as fast as you can. Too fast will send water
over your hood and possibly into your intake. Too slow may flood the engine bay. Hopefully
you follow your line get to the other side with no issues. If you have to
stop, slow or reverse, avoid using the clutch as this may allow water and debris
to get between the friction plate and the flywheel. If you start to loose
traction, its important not to
over-rev the engine. Back-off the accelerator and move the front wheels
side to side a little in the hope that the wheels may regain traction.
If you stall the engine, put the vehicle in neutral
without using the clutch and attempt to restart. If your lucky and you didn't
flood the intake or drench your electrical components the engine will
fire up. Its normally best to use 1st gear low range and with a minimum
of clutch usage, try to get moving again. If you find yourself stalled in the middle of a crossing and
you can not re-fire the engine, depending on the
water depth, its advisable to climb out of your window rather than open the door and flood
your interior including electrical components, seats, gear and carpets.
After encountering a water crossing you want to be sure to
inspect specific things that could be affected by the water. Any time you
encounter a water crossing that is axle
depth or deeper, check the differential oil for water contamination. Even if you
extended differential breathers, this is not a guarantee that water has not
entered the differential. If you do not have differential breathers this
should mean a mandatory inspection. Even though the best time to check the
differentials for water is right after the crossing, most of the time, people
will not check it right there and will continue wheeling the rest of the day.
However checking the differential fluid is relatively easy to do. Since water is heavier than
your gear oil oil, it will collect at the lowest point in the differential,
at the drain plug. To properly inspect it after a crossing allowing time for your
axles vehicle to cool a bit, then loosen the drain bolt and run a small amount of the
gear oil into a glass or cup. You'll see water if it's present. Also a milky
or chocolate milk colored oil
indicates water is present. If
you're unlucky enough to have water present in your gear oil, the differential oil should be drained
and replaced. Driving your vehicle for any distance with water mixed with the
gear oil can damage your ring and pinion. If you had taken on water in the
differential and have to drive out, allow the axle to cool for a while and
attempt to drain as much water as possibly without draining any larger quantity
of gear oil. Collect this oil and water
mixture in a container and save it until you get home, then dispose of it
properly. Never dispose of oil into the environment.
Aside from the axle differentials your gearbox, transfer case and engine oil
can all become contaminated by water. These however usually
only take on water when a vehicle is stationary in deeper water. Also
check other electrical items such as your electric winch. Winches
typically are not used for extended periods of time but when they are needed,
they may have been damaged or may have seized due to the water exposure.
Periodic maintenance and testing should be part of your routine anyway.
After a water crossing give the winch a quick test of it's operation.
Water crossing should be taken seriously. Water has the
potential to do expensive damage to your vehicle's engine and drive train. But
with proper preparation and post inspection and maintenance, the challenge of a
water crossing can be as enjoyable as any other offroad challenge.