How to clean your engine bay

Benefits of Cleaning Your Engine Bay

Cleaning your engine bay is beneficial for a variety of reasons:

Prevents Corrosion

Over time, dirt, grease, and grime can accumulate in the engine bay, leading to corrosion and rust on metal components. By regularly cleaning your engine bay, you can remove these contaminants and prevent corrosion, prolonging the life of your vehicle's engine and other components.

Reduces Risk of Electrical Issues

Dirt, dust and debris in the engine bay can also pose a risk of electrical issues by interfering with electrical connections and components. Cleaning the engine bay removes these contaminants, reducing the risk of electrical problems such as shorts, misfires, and other malfunctions.

Improves Engine Cooling

A clean engine bay allows for better airflow around engine components. If it is covered in gunk it holds in the heat. A clean surface improves airflow and helps to dissipate heat more effectively, keeping the engine cooler and helping prolong the life of engine components.

Easier Maintenance and Repairs

A clean engine bay makes it easier to perform routine maintenance tasks, such as checking fluid levels, inspecting belts and hoses and checking for leaks. With a clean engine bay, a mechanic can quickly identify and address any minor issues before they become major, saving time and money on repairs.

Maintains Value

A clean engine bay is a sign of a well-maintained vehicle, which can help its resale value. Potential buyers are more likely to be impressed by a clean engine bay, as it indicates that the vehicle has been cared for properly and is less likely to have hidden issues.

Cleaning the Engine Bay

Before you start cleaning your engine bay, gather all the necessary materials and tools.

Tools for the Job

• Vacuum cleaner, blower, or air compressor blower
• Degreaser or engine cleaner — Spray can or premix bottle but make it a spray.
• Various brushes of different shapes and sizes — For large flat surfaces or nooks and crannies. Best to look in the engine bay to see what will work best. Not too stiff in the bristles.
• Garden hose or pressure washer — Do not use high pressure water on the engine. Don’t use a jet stream even on the garden hose. Shower or fan is best. Also don’t soak components. A quick rinse to clean off the degreasing agent is all you want.
• Lots of microfibre towels or cloths
• Plastic bag or cling film — To cover sensitive components like the alternator and fuse box.
• Plastic, rubber restorer to give a nice black finish.
• Safety goggles
• Gloves

Prepare the Engine Bay

Start by ensuring that your engine is cool to the touch before you begin cleaning. It's best to clean your engine bay on a warm day when the engine is not hot, as this will help prevent the cleaning solution from drying too quickly and causing streaks. Open the bonnet.

Be Careful of Electrics

Most vehicle electrics are designed to cope with water, provided it is in good serviceable order (covering is not cracked or broken) and you are not pouring water over it with a bucket. A quick spray so the water does not have time to soak in will not hurt it. Some people disconnect and remove the battery, and this may be a good idea for older cars.

New models are not so forgiving if the battery is disconnected. If the main battery terminal has a good cover cap, it will be OK to leave it connected. If you are worried, cover the top with a plastic bag. Cover sensitive components such as the alternator and air intake opening with a plastic bag or cling film to protect them from water and cleaning solution. Anything you cover can be wiped later to clean it.

Dealing With Leaf Litter

When cleaning, start from the top and work your way down, no different from washing the outside of your car.  Start with under the bonnet, then around the edges of the engine bay and finally the engine itself. On smaller cars you may clean the engine and engine bay in one go.

Before wetting or spraying, use an air blower or vacuum cleaner to clean up any leaves or debris around the edges of the engine bay. The ventilation intakes near the windscreen usually trap a lot of leaf litter. This is best done dry as wet leaves stick to surfaces. If it has not been done for a while a dry brush may help loosen some of the debris.  

Under the Bonnet

On painted surfaces, degrease, agitate if needed, and hose off. Most bonnets have insulation covering the underneath to reduce noise and keep hot engine temperatures from affecting the outside of the bonnet. Take care when cleaning these as some can soak water which will cause them to sag.  A carpet cleaner can be used on these, though you should test it on a small patch first before spraying the rest of the bonnet.

Around the Edges

Use the degreaser or cleaner around the edges of the engine bay.  In areas where the grime is thicker or more caked on, agitate it with a brush. Use different size brushes to get into the nooks and crannies. Some places you may need to revisit after you have given the degreaser more soaking time. Don't let the degreaser or cleaner dry onto the surface so use it liberally or hose it off. Work areas in sections to help stop this. Around electrics like a fuse box or relays use the degreaser and water more sparingly.

On the Engine

Use the same process for the engine as you did the areas around it. There can be large plastic covers over the engine. Once the tops of these are cleaned you can remove them to check underneath to see what else needs cleaning. Different size brushes help get into the hard-to-reach places. Take care around sensors or anything that has a wire connected to it as you don’t want to break it off by brushing too enthusiastically. Before drying, it is a good opportunity to inspect your work and touch up any area’s that you feel need more cleaning.

Drying the Engine Bay

Once you have cleaned the engine bay, engine and thoroughly rinsed or wiped away the cleaner or degreaser, it is time to dry things off. Using an air blower or wet and dry vacuum remove most of the water. Any residual wet areas you can wipe away with a microfibre cloth or rag. Even paper towel. You simply want to remove as much water as possible before starting the engine.

Touch Up

Once the engine bay is dry, you can remove any plastic coverings you put over vital components. You can give these components a clean by spraying cleaner or degreaser on a rag or cloth and wiping the grime off them. Finish off with a clean rag or cloth. Replace any plastic panels and reconnect any disconnected items. There are plastic and rubber restorers you can use to make the engine bay look new. They are usually spray on, let soak or dry and gentle wipe off any residue with a clean towel.

Start the car and let it idle for a number of minutes. Let the engine warm up as engine heat is a good way of getting rid of any water or damp area’s you missed or couldn’t reach. Once warm close the bonnet and take it for a drive just to check it is working ok.

Regular Maintenance

To keep your engine bay looking its best, it is important to perform regular maintenance and cleaning. As a guide, maybe once every 6 months. A lot depends on the number of kilometres you drive and the environment in which you drive, you may need to clean your engine bay more frequently. Be sure to use a quality degreaser or engine cleaner and avoid harsh chemicals or abrasive cleaning tools that could damage sensitive components.

By following these steps carefully and taking the time to properly clean your engine bay, you can maintain your vehicle's appearance and performance for years to come. Whether you're preparing for a car show, part of routine maintenance, or simply wanting to take pride in your vehicle's appearance, a clean engine bay is a worthwhile investment that pays dividends in the long run.