Fault Diagnosis Is an Art Form
While we all want to save a little cash by self-diagnosing a mechanical issue and proudly gloating over a DIY roadside fix, it's not worth it if you hurt, injure or, at worst, kill yourself. As terrible as it sounds, it can happen. It only takes an ill-positioned jack to fall, contact with a high-current electrical wire, a scald from a steaming radiator, or a poke in the eye by an errant stick, wire, or mechanical part. Of course, a bit of bark off your knuckles is bound to happen from time to time. It's the major hazards you need to avoid.
My advice: if you're not sure what you're doing or sense a hint of danger, then don't do it. Don't put your body or life on the line. Ask the professionals for help.
Tackling it yourself
Fault diagnosis is an art form. While it can be learnt from experience, through training, or even passed down by parents and grandparents, there are a few basics that can help identify the origin of a fault. You may not be able to repair the fault, but identifying it might help you decide whether you should keep driving, work on the problem yourself, or call on the experts to help.
In general, I put faults into two categories: ones that you can see and ones you can't. For the ones you can see, like a loose tarp flapping while you're driving or a rope or tie-down strap clanging on the side of your vehicle, the fix is easy. Tighten them, return them to how they should be, remove them completely or break out the roll of ‘hundred-mile-an-hour’ tape to hold it all together.
As for the faults you can't see, there are a few basics to help track down the root cause. Initially, I like to know how quickly the noise is occurring and relate it to the car's speed, as well as the engine and driveline revolutions. For each revolution of your wheel, can you hear the noise (or problem) once, twice or multiple times? Knowing this basic rhythm and mechanics might tell you the noise is coming from a wheel bearing or brake component (within the wheel), the diff, tail shaft or motor.
For example, perhaps there's a piece of wire or a stick wrapped around the tail shaft. As you drive slowly forward, you'll hear the noise multiple times for each wheel revolution. The same goes if the noise is coming from the diff.
If that noise increases in frequency when you rev the engine without the car moving, then the problem is within the engine or perhaps part of the gearbox. If it happens when you push or release the clutch pedal (with manual gearboxes), then there's a high chance your problem is part of the gearbox (pressure plate, flywheel, release springs, spigot bush, etcetera), or if you're lucky, one of your kids' toys has just jammed under the foot pedal!
Does the noise happen when accelerating, decelerating, turning left or right, uphill or downhill? How about when the vehicle is being driven versus free-rolling down a slope? Where you find the noise occurring and when or how fast it happens will determine how easy a roadside fix might be, or whether you can drive to your nearest mechanic.
Tune in to your senses
A healthy dose of common sense is often required when diagnosing problems. Using your sight, hearing, touch and smell will go a long way to helping you narrow down the issue. Can you see the loose part flapping in the breeze? Can you hear it making a god-awful noise, keeping in mind sound can travel far from the source? Can you feel something loose or out of place? Can you smell the clutch or brakes burning, the engine overheating or something smouldering that might be electrical, rubber or perhaps the oven left on in the caravan?
Take the time to stop, investigate the situation and use all your senses before doing anything else
Tricks of the trade
A length of hose (roughly half a metre long), a mechanic's stethoscope, or even a piece of timber can be used to pinpoint noises and problems. Simply holding either on or near a moving part (spinning wheel, running engine or moving car part) can often pinpoint the problem.
Locating a collapsed wheel bearing on a trailer with a length of hose is relatively easy. Jack up one wheel, spin it by hand, and hold the hose near the hub to confirm where the noise is coming from. Same goes for the stethoscope; just like listening to a heartbeat, it can be used to listen to fuel lines, injectors, internal engine components and differentials. There's no need to know exactly what these components should sound like. Rather, you're listening for differences or changes in sound. Does one injector sound different to the others? Does one wheel bearing sound different to the others?
A non-contact thermometer, or even your hand, can be used to detect a problem via temperature sensing. I'm not suggesting you need to know what temperature any part of your vehicle should be; rather, the key is to find a difference. For a dual-exhaust car, for example, try placing your hand (carefully) on each exhaust outlet and see if they are roughly the same temperature. Use the thermometer to measure each exhaust manifold pipe or cylinder while the engine is running. All you're looking for is a difference from one to the other. A few degrees difference here and there is no problem, but if one cylinder measures significantly different from the others, then my bet is that something is going wrong inside your engine.
Always keep in mind your safety: watch out and keep away from spinning and moving parts such as fan blades, engine-driven belts and linkages, they can all do serious damage.
Unless you're sure of the exact problem and can fix it, you're often better off showing or telling a mechanic where, rather than what, the problem is. Telling them your diagnosis might be misleading. At least if they know roughly where to look, along with the sound, smell and other signs, they can expertly diagnose the problem and suggest a fix.
It all depends on how mechanically adept you are, what tools you take on the road and how dirty you want to get by the roadside to make the fix yourself.
Preventative DIY monitoring
As well as keeping an eye on your dash-mounted warning lights when driving, take the time to look, listen and feel the various parts of your vehicle when it's in top-notch mechanical condition at home. Jack a wheel up to listen to the bearings. Break out a piece of hose to listen to engine components. Measure the temperatures of different parts of the driveline; something as simple as holding your hand to your tyre and rim every time you pull up is a surefire way to spot an early failure. That one time you feel more heat than expected is the time you'll save money, inconvenience and the pain of a remote-area fix.
Happy motoring, and remember to keep all your senses active to ensure early warning signs aren't missed.
