Identify these key noises and you may just save yourself some cash...

With the increased cost of just about everything these days, we all know how a limited maintenance budget can suffer with unexpected automotive repair costs. Now, more than ever, preventative maintenance is a smart exercise that can save you a considerable amount of money down the line.

Here are some guidelines on how to diagnose three main categories of noise that, once determined, will steer you in the right direction for identification. They are noises that:

• Increase with car speed and are related to wheel problems.
• Increase with engine speed and involve the engine.
• Random noises that are not related to either engine or car speed; likely suspension or road-related problems.

Noise 1: CV joints

Constant-velocity (CV) joint wear on front-wheel-drive cars is quite common. The innards of a CV joint are operational when the wheels are at an angle during cornering (driving straight does not usually result in any noise or knocking). If you notice grating or knocking noises when turning left or right, this is most likely wear in the balls and tracks caused by dirt entering the joint via a cut in the rubber boot.

Although hearing these sounds means that the joints are already at an advanced state of wear, specialist CV joint repairers are able to fit a new part in a short enough time and at a reasonable cost. Much better still is to regularly inspect the protective boots that keep the grease in and the dirt out. This way, when you see a tear in a boot, you can immediately go to the workshop and pay only for a boot replacement and not the entire joint.

Noise 2: water pump or slipping belt

This is a high-pitched squeal originating from under the bonnet and inevitably points to a failing water pump. If the pump is reachable, try to wiggle it to check for play. Plus, look for signs of leaking coolant under the car.

The other possible cause is something altogether simpler, such as a slipping ancillary drive belt, so first check for correct tension. If not treated timeously, a worn or damaged pump can fail and this will lead to loss of water, possibly overheating and then severely damaging the engine.

Noise 3: the wheels

One of the most difficult noises to pinpoint is a droning sound linked to the car’s speed. This could be tyre-tread noise or wheel bearings on the way out. From inside the car, it is often difficult to hear which wheel is causing the problem. Trial and error may be the only way to solve the issue. Try swapping wheels to check if there is any change. You can also jack up the wheels and rotate them freely to listen for signs of worn bearings. Check the tread for uneven rubber wear or alignment problems. Another possibility is to connect the car on a rolling-road dynamometer and have someone listen to each wheel as it spins to pinpoint the culprit.

Noise 4: bearings

Another under-bonnet noise is a low-pitched rumbling sound due to a worn bearing. Accurately locating the source of the noise requires a stethoscope or length of tubing applied to each belt-driven ancillary in turn, including the alternator, power-steering pump and air-conditioner pump.

Noise 5: wind

Wind swirling around various elements such as the front grille, air dams and headlamps creates a noise and this increases with speed. It’s usually eliminated at design stage using a wind tunnel. If your vehicle is therefore exhibiting excessive wind noise, it may be the result of an aftermarket accessory such as spotlamps, or possibly due to slight frontal accident damage. Solving this will involve trial and error, perhaps using applied duct tape to pinpoint the culprit.   

Five other culprits...

1. A chuffing sound like compressed air 
Look for a hole in the exhaust, or a blown manifold gasket.

2. Groaning sound when turning the steering wheel
Most likely a steering-pump bearing failing.

3. High-pitched squeal when applying the brakes
Worn-out pads are the cause.

4. Rumbling, grinding sound that comes and goes
Check that the wheel nuts aren’t coming loose, especially on the left side due to the wheel rotation.

5. Wind noise from the doors and windows
Check the dust seals. They are often not glued in place and can easily come adrift.