What's Under A Car Bonnet?

Posted by Motorama in Servicing Tips

It's easy to think you know everything there is to know about maintaining your car, but you may be missing some vital components hiding under your bonnet.

While a good car service centre will take care of any problems you have under the hood, it's still a good idea to get to grips with your car's engine and a few other components you may be unfamiliar with.


One of the most obvious and important pieces in your car is its engine. At the core of the engine is the cylinder, which has a piston moving up and down inside of it. Most cars have more than one cylinder, with four, six and eight cylinder engines the most common. Multi-cylinder engines have cylinders arranged in inline, V or flat formations.

The different configurations have pros and cons in regard to manufacturing cost and operating smoothness. Also contained within the engine are intake and exhaust valves, which open to let air and fuel in and get rid of exhaust. Spark plugs are also vital to ensure the engine runs correctly, as they supply the spark that ignites the air/fuel mixture at just the right time in order for combustion to occur.

Fitting into the mix are piston rings, which provide a seal between the piston and the cylinder wall. The rings slide with the piston, and help stop the combustion chamber's air/fuel mixture leaking into the oil sump during compression and combustion. They also keep the oil confined below the combustion chamber so that it doesn’t get burnt up during the combustion process. There's a connecting rod, or conrod, to connect the piston to the crankshaft, which is then connected to the gearbox via an input shaft.

The conrod can rotate at both ends, shifting angles as the crankshaft rotates and piston moves up and down.

Brake fluid

You'd be surprised at how much impact brake fluid can have on the health of your car. The liquid transfers the force from when the driver pushes the brake pedal directly onto the brake rotor and therefore the wheel hub. Heavy and prolonged braking can generate a lot of heat, which can affect the liquid.

Brake fluid will only work if it is in liquid form and not so hot that it has vaporised, which can result in brake failure and ultimately an accident. The fluid can work as a lubricant of moving parts and may prevent corrosion.

Brake fluid is hygroscopic, which means it attracts and soaks up water. If you think there's a problem with your brake fluid, get in touch with the team at Motorama, who are experts in car servicing.

Transmission oil

Transmission oil can often be overlooked, but it is vital to ensuring your car is properly maintained. The oil transfers the engine's power to the vehicle's wheels, and coats gears and torque converters. The majority of modern cars have an automatic transmission that requires automatic transmission fluid (ATF).

Pressure changes in the ATF are what triggers the transmission to switch gears. It's generally advised by manufacturers that car owners change their ATF and filter every 32,000 - 40,000km.This is because many driving conditions, including stop-start driving, towing heavy loads, long distance driving and driving up and down steep inclines, can cause transmission fluid to overheat and break down.

This means your transmission can have difficulty shifting gears.

Windshield washer fluid

While this may not be as vital to your car's mechanic capability as the other components mentioned, you should still pay close attention to the level of liquid you have available to wash your windscreen on the go. Dirty windshields can be extremely hazardous, so make sure your fluid is topped up at all times.