A clean engine compartment makes repairs or maintenance easy. If it's been a long time since you've cleaned your engine, you'll need to give the degreaser time to soak in the dirt and work hard to remove the grease deposits. It's best to clean the engine and under the hood before washing the car to make sure you wash and rinse off any degreaser that could get on the painted parts. Cleaning the engine regularly prevents rust. Dirt and road salt are the main culprits for rust, so washing under the hood will extend the life of the engine.
Method 1 of 3: Protect and Prepare the Dirty Engine
Step 1. Remove any debris from under the hood
Before you start cleaning the engine, remove leaves, grass, branches, and other debris from under the hood. These can become a problem and even cause fires if left in the motor or electrical system for too long.
- It is common for tree leaves to stay on the bottom of the windshield and then fall under the hood.
- Look for small animal nests, especially when the weather turns colder.
Step 2. Disconnect the battery
Spraying water directly under the hood could cause some electronics to spin, blown fuses, and other damage. You can avoid them by loosening the screw on the negative battery terminal and sliding the ground wire off the terminal.
- You can also disconnect the positive terminal to remove and clean the battery outside the engine compartment.
- If you leave the battery in the vehicle, tie the ground wire aside to prevent it from coming into contact with the terminal.
Step 3. Cover exposed wires and electronics
While the motor is nearly waterproof, wrapping some electrical parts in plastic offers added security. Covers spark plug gaps, loose wires, and distributor cap if your vehicle is equipped with one.
- Small plastic bags or kitchen wrap works as protection against water.
- Check your vehicle's service manual if you're unsure if it comes equipped with a dealer or if you don't know where the spark plug gaps are.
Step 4. Leave the engine running for 5 minutes
The grease on the engine will be easier to remove if it is hot. Start the vehicle and leave it like that for 5 minutes or more. This will allow the engine to come up to normal operating temperature and loosen any sticky dirt.
Don't leave the engine running too long or you could burn yourself when you start cleaning again
Method 2 of 3: Degrease the Engine
Step 1. Apply motor degreaser
There are many brands of degreaser you can choose from, but most work the same way. Spray the degreaser on the engine from the bottom up to ensure full coverage.
- Most degreasers come in a spray bottle for easy and simple spraying on the engine.
- Read the instructions on the degreaser you buy to make sure you are using the best method for that particular cleaner.
Step 2. Avoid getting degreaser on painted parts
Engine degreaser can remove layers of paint, so be careful not to spray too much when covering the engine. If degreaser gets on the bumper or other painted areas, rinse it off quickly to avoid damaging the paint.
- Degreasers can remove the shine from car paint.
- Rinse the degreaser off painted surfaces as soon as possible.
Step 3. Allow the degreaser to absorb for 3 to 5 minutes
Engine degreaser works by removing accumulated dirt. For not-so-dirty engines, three minutes is enough to loosen stuck grease and oil. For really dirty engines, leave the degreaser on for a full 5 minutes before rinsing.
- If the instructions for the degreaser you choose set a different time, follow the directions on the bottle.
- The longer you leave the degreaser on, the better results you will get.
- After five minutes, the degreaser will start to drip from the engine.
Step 4. Use a stiff bristle brush to scrub stuck dirt
With the degreaser on the engine, use a stiff bristle brush or a steel brush to scrub off any grease deposits, burnt oil, or dirt. They will loosen quickly thanks to the degreaser.
- Wear safety glasses while scrubbing the engine to avoid getting degreaser in your eyes.
- Wear gloves to avoid prolonged skin contact with the degreaser.
- Only scrub the engine if it has a lot of dirt stuck to it.
Step 5. Rinse the motor with a normal hose
Do not use a high-pressure hose to flush the motor because it could disconnect cables or penetrate the plastic bags you placed to cover the electronics. A normal hose stream will effectively flush the engine and remove most of the dirt.
If you rinse the engine completely and it still looks dirty, apply the degreaser again and leave it on for a few more minutes
Step 6. Wash the car
Once you've flushed the engine, you should start washing the car right away. This will remove all the degreaser from the painted parts before causing any significant damage.
- Make sure to use a different bucket, sponges, rags, and towels to wash the car.
- Use wax on all areas of the car that have come in contact with the degreaser.
Method 3 of 3: Clean Specific Engine Components
Step 1. Use a metal brush on the battery terminals
The battery terminals suffer from corrosion, which can cause problems with the vehicle's electrical system. Remove the battery cables and use a metal brush to scrub the terminals until they are clean and the metal can be seen.
Soaking the battery cable tips in an anti-corrosion chemical like CLR also helps to ensure a solid electrical connection
Step 2. Apply baking soda and water to the battery acid
If the battery has corrosion from a battery acid leak, you can neutralize it while cleaning by using a combination of baking soda and water. Pour some baking soda into a bucket of water and mix carefully. Dip the brush into the mixture and use it to scrub the battery terminals and any areas the acid has touched.
Baking soda is an effective cleaning solution and is also good for neutralizing battery acid
Step 3. Use a stiff bristle brush and sponge for the plastic parts
Plastic parts like engine covers and tank lids can be difficult to scrub. Start with a stiff-bristle plastic brush with car soap or degreaser. Once stubborn dirt has been removed, use a sponge with car soap to remove the rest of the dirt before rinsing the parts with water.
- You can remove the parts for cleaning outside of the engine compartment, but it is not necessary.
- Do not use steel brushes on plastic as you could scratch it.
Step 4. Use brake cleaner to clean dirt deposits
Brake cleaners cut and evaporate dirt quickly. Insert the straw into the nozzle of the cleaner and direct it towards areas where the dirt is very thick. Use a stiff bristle brush to scrub, then spray the brake cleaner again to rinse.
- Be careful with brake cleaner indoors as the fumes can be dangerous.
- Brake cleaner is extremely flammable, so don't use it if you're smoking or flames are nearby.