Water Crossing 101: Part One
As a principal guide for CO, this, of course, takes my thoughts toward the eleven water crossings which are in store for participants of April’s “High Water Mark” event. But beyond our trips, I know that many of you will find yourselves up in the mountains this spring just playing and enjoying the gorgeous surroundings on your own. As is often the case within the Ozarks and Ouachitas, you may find yourself also having to ford a river or creek in your truck or SUV. I want to take this week to share a few basic thoughts about waters crossings before the wet season gets going in full force.
First and foremost, if you don’t have a snorkel and elevated breathers, don’t worry. Nine times out of ten you simply don’t need any modifications to a reasonably capable 4WD vehicle. (I hope my retail sponsors forgive me for that candor!) Since most folks will never significantly modify their vehicle, this is the audience I am addressing in this blog.
Almost every 4WD truck and SUV can be driven in water that is axle-deep without taking special precautions. A good rule of thumb is simply taking a peek at your hubs. (The smallest circle at the innermost of your wheels, just within the lug nuts.) If you drive slowly and keep the water below this level, then you will have zero problems. For some larger vehicles, this may provide up to fifteen or more inches of available fording capability direct from the showroom floor. Folks, that’s pretty good! Issues arise as one ventures deeper, but proper understanding of the potential risks, their mitigation techniques, and some basic off-road driving skills can really help when the time comes to go for a swim.
When drivers think about fording deep water — which, for the sake of this blog, we’ll say is anything beyond the hub depth I described a moment ago — their mind often considers first the engine’s air intake. This is an understandable concern, as that intake basically serves as a large vacuum drawing fresh air into the motor. You submerge that thing, and you have yourself a 4″ wide drinking straw. That, my friends, is the fastest way to hydrolock your motor. But I digress into territory which I’ll cover later. No, what is generally the first risk is often the most overlooked: drivetrain breathers.
As you drive your vehicle, the moving parts cause friction which generates considerable heat. That heat, as we all remember from 7th grade science, expands, and as it does, that pressure must be allowed to escape. Vehicle manufacturers place “breather valves” throughout your drivetrain to allow this to happen; the front and rear differentials, the transfer case, and the transmission each get one. Very often, it’ll be an innocuous looking little metal cap, sometimes bolted into the drivetrain component itself, or sometimes connected to that component by a hose in an effort to get it as elevated as possible.
As you enter a cold river with a hot differential, the air inside of that axle housing will immediately contract. This contraction will only last a very short period of time, but during which, opposite to the initial heating, air will re-enter that breather valve and occupy space in the axle housing. The same is true for each of your drivetrain components. See the problem here? If you’re breather valve is underwater during this contraction, well, your diff just got a gulp, and now your lubricating fluids are nice and milky. If you don’t get that fluid changed as quickly as possible, things can get expensive in a hurry.
The best mitigation technique for this risk is very simple: drive slowly. By entering the water slowly, you allow the largest part of the contraction to take place before the vehicle reaches water depths which would cause any potential harm. Keeping speeds at about 1-5 mph during the submerging will close to eliminate all hazards associated with thermal contraction. Like I mentioned before, it is a relatively quick process, generally lasting only a few seconds.
However, if you’ve identified that your breathers are not suitably high enough from the factory for the crossings you’re certain to encounter while overlanding, and if this is going to cause you to have a breather cap fully-submerged for any length of time, it’s probably a good idea to go ahead and elevate them to a point as high as reasonably possible prior to your next big trip. This is a basic job requiring basic skills and tools. It costs only a few bucks but it could save you hundreds. There are a lot of write-ups on the subject throughout the internet.
During Parts Two through Four of this series, I’ll speak more about the engine, its air intake, associated water risks, and the mitigation techniques for ensuring that the powerplant you’re dependent upon to get you safely back to shore doesn’t become a carrying device for a few gallons of that river’s lovely mountain water. Finally, Part Five will focus on driving techniques and considerations you’ll want to keep in mind when faced with your own amphibious assault.