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4 September 2024 What is under a car bonnet?: what to check
What is under the bonnet of a car?
You’ll find most of the critical car components that power your vehicle as well as its electrical and safety systems inside the car bonnet. For example, if you open up the bonnet, you should be able to spot your engine in the engine bay, the car battery and alternator, the radiator, and the fuse box without much difficulty.
Those who are just starting to drive or maintain a vehicle by themselves can feel a little overwhelmed at first. This is why it’s important to start with the most basic parts of car maintenance, which also require regular servicing. Check your vehicle model’s repair manual for the exact location of these components or a detailed car bonnet diagram.
What to check under the bonnet:
Engine oil reservoir
Motor oil is the lifeblood of any internal combustion engine. It acts as a protective film for the moving parts, preventing premature wear, thermal damage, and corrosion. It is important to change the oil regularly according to your vehicle’s maintenance schedule (usually every 5,000-10,000 miles or every 6 months) as the oil will eventually deteriorate and be ineffective.
You should also regularly check the oil levels in the reservoir to ensure that there are no leaks or faults in the system. First, you’ll need to locate the reservoir and oil filler cap. You should see an engine oil symbol under the bonnet. This looks like a small oil can and/or is sometimes labelled “engine oil”.
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You can check the oil levels using the car’s dipstick (if it has one), which is normally right next to the reservoir and has a yellow ring at the top. Some modern cars use an electronic oil monitoring system instead.
Remove the dipstick and wipe it clean with a clean old cloth or paper towel. Reinsert it and remove it again to check the readings. The oil level should be between the “Min” and “Max” markings. If the oil is brown or smells burnt, it is time to change it.
Engine coolant
Due to its high operating temperatures, the motor needs coolant fluid to prevent it from overheating, to stop the car engine parts from deforming or melting, and to prevent scale buildups. The brightly coloured fluid consists of a mixture of antifreeze and water.
You can usually find the coolant reservoir next to the engine block as it sends fluid directly to the unit. There should be an engine coolant symbol under the bonnet on the tank cap indicating where to check and top up the fluid, or sometimes the word “coolant” will be written on the reservoir cap. You should only use the type of antifreeze specified by the vehicle manufacturer and never mix different types.
Make sure the coolant level is between the minimum and maximum marks. You should also inspect the fluid for signs of contamination such as debris, rust particles or discolouration as this can negatively affect the cooling system.
Car battery
Standard car batteries are expected to last around 3 to 4 years before they need to be replaced. Unfortunately, over time they will age and become less efficient, just like us. If you’re having power issues, make sure to check whether the terminals are loose or corroded and for any signs of damage or leaks.
Batteries tend to last a bit longer in cooler climates as the cold slows down chemical reactions and therefore slows degradation. You can also make your battery last longer by avoiding frequent short car journeys and making sure to turn off all electrical components, including the radio and lights, when the engine is switched off.
Windscreen washer fluid
The windscreen washer fluid is needed to keep the windscreen free of dirt, grime, snow, and ice to ensure that you’re able to see clearly while driving. It’s important to keep it topped up, particularly before long car trips. The reservoir is normally near the engine bay and just below the base of the windscreen.
Bonnet faults
If the car bonnet itself is broken or won’t lock into place properly then there is a higher risk of damage or corrosion for the parts located underneath it. It could also become loose while driving, potentially reducing your visibility and causing an accident. This is why you should replace it as soon as you can. Check the online shop for more information on replacements and car bonnet prices.
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