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I am writing a book on vehicle based expedition travel through The United States and Canada
This page contains a draft excerpt from the section about trail driving
Copyright 2007 - 2009 by TeriAnn Wakeman all rights reserved.
No part of this page can be reproduced without expressed permission of the author
Water crossings
Water crossings are always easiest when you are not the first vehicle in a group to cross. Always pay careful attention to where the leading vehicles of a group plant their wheels and how they fare. If they have trouble and you can not see why by reading the stream it is best to get out and walk the stream to get a feel for it. If you are alone at a crossing with no one to pull you out in case of trouble I strongly recommend that you walk the crossing first to learn the depth and get a feel for the bottom.
Water crossing preparation begins at home. The first thing you need to know is the vehicle manufacturer’s recommendations for wading. Purchase and use any special parts recommend by the factory such as wading plugs, baffles or covers. Axles and many gearboxes have breathers to keep internal pressures from building up and pushing oil past the seals. Most breathers can be replaced with an assembly that has a long tube that opens to air well above the maximum wading depth. This modification will go a long way towards keep water out during deep crossings.
You need to learn why the manufacturer set the maximum wading depth where they did. Often it has to do with the location of electrical components such as alternators, relays, engine sensors or computers. Alternators, relays and computers can be remounted to a higher location but sensors pretty much need to stay where they are. Engine sensors are usually at the engine operating temperature and tend not to take well to the sudden thermal stress of being submerged into water 150 degrees or more colder.
Newer engines usually have a crank angle sensor located on the same horizontal plane as the center of the engine crank. If it should break from sudden thermal shock the engine will stop and cannot be restarted until the sensor is replaced. It is always a good idea to always cary a full set of replacement sensors for electronic controlled engines and maybe two each of the lowest placed ones.
On older gas engines the deepest wading depth is often the level where water can reach the generator or alternator if they are mounted low on the engine. Fabricating new mounting brackets and mounting the alternator at the top of the engine will cure the . Next in line is usually the distributor. A few decades back wading kits that consisted of rubber boots for the distributor and spark plugs were popular. They were hard to install and usually deteriorated quickly inside the engine compartment. They almost always leaked if the distributor was submerged but did provide good splash protection.
You can get almost as good splash protection by running a bead of RTV around the seam where the cap meets the distributor and follow that up with a couple tight wraps of electrical tape. This is a short time fix that should be added a day or so before the crossing and not something that should be left on all the time.
Air filter intakes should face away from the radiator. Water does not compress and can break an engine faster than you can turn off the ignition switch when you notice a problem. A sealed snorkel can protect against engine damage from an unexpected deep dunking.
A vehicle in motion creates a bow wave at the front and the water inside the engine compartment will be at a lower level than outside the vehicle. Ideally you want a small bow wave. When wading streams with solid bottoms you should be moving at around 3 MPH and be in a low enough gear so that your engine is in its torque power band. You want to go about twice that speed on a soft sand bottom or when you need to rely upon momentum to get you up a steep embankment or through a momentary deep spot in a fast current. Driving fast through a crossing throws a high wave that impresses the photographers but is likely to leave you dead in the water with a wet distributor. A word of caution at water crossing photo opts. People like to have their headlights on while throwing water as high as they can for the camera. Headlamp glass can get very hot and may crack if suddenly hit with a solid wall of cold water.
The water right behind the bow wave is lower than the surrounding water and helps protect your engine compartment. You can increase this affect by putting a barrier in front of the radiator opening. A small plastic tarp or a regular cold weather radiator muff can make a big difference in the water depth inside the engine bay during a deep water crossing.
Never, if you can help it, stop the vehicle when in deep water. Within a second of stopping the water level inside the engine compartment will equalize with the level outside and may drown the engine. Exhaust pressures keeps water out of the tail pipe, mufflers and catalytic converter. These areas will flood if the engine stops in deep water. If you absolutely need to come to a halt in deep water shut of the engine before you stop and get towed out.
A major source of water problems in an engine compartment is caused by splash from the radiator fan. It can do a great job of slinging water into the engine’s air intake, distributor and the rest of the electrical system. If you have an electrical fan the cure is to add a driver operated on off switch for the fan and just shut it down for the crossing. Your best bet for a long deep crossing with a mechanical fan is to have splash baffles in place that redirect fan spray away from the intake and electrical parts.
Before making a moderate to deep crossing it is a good idea to make sure that any special wading gear is in place, that you have a cover over the front of the radiator opening and that important or easily water damaged items inside the vehicle are located in a high place. Secure one end of a tow strap to your vehicle’s tow ring in the direction you are most apt to receive a tow from and secure the free length somewhere it will be above water and out of the way during the crossing. This will save you from having to feel around underwater for a tow point if your vehicle gets stuck during a water crossing.
When making a deep crossing it may be best to think of your vehicle as a very leaky boat on wheels. If the water gets deep enough your vehicle will tend to float. This means less traction to your wheels that are trying to find a grip on a wet and often loose bottom. In addition the flow of water will be trying to push your vehicle downstream. Making a deep water crossing broadside to a strong current is just about the worst thing you could do behind trying to cross a silt bottom. Whenever making a crossing in a fast current deep enough to put the vehicle body into the water you should make the crossing at least 45 degrees to the current, preferably going in the downstream direction so the current helps you get across.
Reading the water:
The old adage of still waters run deep is indeed true. The surface of the water can tell you a lot about what the bottom is like. That and the shape of the stream bed at your proposed crossing point can give you a very good idea of the crossing. Anytime you have any doubts about the crossing, especially the depth the best thing to do is wade the crossing on foot before driving it. The depth of very clear water can be deceiving.
A flat water surface tells you that either the water is deep or the bottom is flat sand. Be very wary of driving through a section of water with a flat smooth surface. If you are the first or only vehicle at a flat surfaced water crossing you will want to walk across first to verify depth and bottom type before attempting to drive across. If the current is sluggish the bottom may be silt which will not support vehicle weight and may quickly sink the vehicle to the frame. Unlike wet sand above water, sand underwater does not hold vehicle weight well. If you are going to cross a sand bottom it is best to go diagonally down stream so that the water current will help move the vehicle along. Keep your momentum up during the crossing. You will want to choose a low gear that keeps your engine’s RPM well within the power band without going too fast for conditions. Do not attempt a silt bottom.
An even rippley surface normally indicates shallow depth with a gravel or small rock bottom. This is your ideal surface for a crossing.
A stationary water bump indicates a largish submerged obstacle that could cause undercarriage damage or hang the vehicle up during a crossing. The water is always deeper directly behind the standing bump. Avoid driving into or behind one.
When a stream bed is straight it is normally shallow towards each side and deepest towards the middle.
A curved stream bed is always deepest along the outside curve bank and shallowest along the inside curve bank. Much of the time it is quite shallow for most of the width with a deep trench and steep bank slope right along the outside bank. Usually the water along the outside edge of a stream curve is deepest at the sharpest part of the curve and to the rear of it. The bank along the edge is usually steepest there as well. If you have to cross at a stream curve try to cross upstream of the sharpest part of the curve if at all possible and make sure you have momentum going into the deep outside curve area.
If you need to travel up or down a stream or shallow river it is best to read the surface and the shape of the stream, keep to the pebbly water surface wherever you can, stay away from the larger standing waves, stick to the side of the stream when it flows straight and take a curve on the inside. Try to avoid crossing broadside to a fast current. An angled crossing presents a smaller area for the current to press against.
After the crossing:
During moderate and deep crossings water will get into tie rod ends and U joints. It is a good idea to regrease all these joints within a day or so after water crossings. Water can get into gear oil reservoirs such as differentials and gearboxes during deep crossings as well. The water can cause damage to these assemblies over time. It is best to check for water in the oil afterwards. Water mixed with oil will resemble a light brown sludge. Opening the oil reservoir drain tends to be a messy procedure with a high possibility of spillage. An easier way of checking is to open the fill plug and use an improvised dip stick to draw out enough oil to check for color. If you find water mixed with the oil drain the oil into an empty can and refill with fresh oil.
Engines that stalled during a deep wade should be restarted very carefully to avoid damage. First pull spark plugs on a gasoline engine then spin the engine over to get rid of any water that may have entered into the cylinders. Replace the spark plugs making sure that they and their connectors are dry.
Check for water in the oil sump by removing the dip stick and checking the color of the oil. If you suspect water, drain the oil into your empty catch can replace with fresh oil and replace the oil filter before trying to start the engine.
If your engine has a distributor, remove the cap and check the inside for moisture. Drying out wet electrics is where a 12V hair drier becomes a very useful part of your kit. It will chase out the moisture without leaving an oil residue behind like some other methods do.
Try to start the vehicle. If it does not start reexamine and dry connections in the ignition system and any computer control system. If the engine is computer controlled check the sensors over closely. It could be that you will need to swap out sensors and controllers one at a time to find the damaged part. There is a reason why modern engines tend to have a low specified wading depth.
Tips for Treading lightly
Avoid seasonal streams, small springs and small pond water crossings in arid areas when you can. These seasonal bodies of water support delicate ecosystems that live in the mud or carry out part of their life cycle in the seasonal ponds. Rough crossings that throw up a lot f water and muddy the water can significantly damage the local ecosystem. And don’t forget standing waters tend to have deep fine sediment that can not support a vehicle’s weight.
Try to avoid muddying waters that salmon and trout spawn in during the spring. Silt carried downstream can bury the fish eggs and kill them. course gravel, flat rock slabs and small river rock bottoms not only provide the best support for your vehicle as you cross but produces the least amount of silt.
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