After the winter, many drivers will wash, wax and detail their vehicles, but many forget to pop the hood and tackle the accumulation of dirt and debris that may have built up over the winter months. Taking the time to clean the engine can help the car run better and prevent unnecessary wear to the various materials and parts.
If your engine is particularly dirty, you may want to turn it on and let it warm up a bit before you start cleaning it. This can help loosen some of the dirt that may be really caked on. Don't let it run very long, or it could get too hot and you won't be able to touch it, let alone remove the grime. After a minute or two, shut the engine off and disconnect the battery, starting with the negative wire and then removing the positive terminal cable. This is the perfect time to clean the battery if you notice any corrosion or acid around the terminals. A stiff brush can be used to remove this buildup.
Next, you'll want to protect the wires and other electrical components by covering them with plastic bags or other waterproof material like cling-wrap. This will prevent them from being damaged while you're washing the other parts. You will need to do the same thing with air vents, as getting water in them can cause serious problems. You can use plastic wrap or aluminum foil for these parts. Tape the edges of everything you've wrapped to ensure water cannot leak in.
Now it's time to tackle the road salt, dirt and whatever else has gotten lodged in the underbelly of your vehicle. First, use a hard-bristle brush to sweep away any loose debris. Then you'll want to coat the motor with an engine cleaner and let it soak for a while. The owner's manual should contain information about which cleaners can safely be used for your car's particular engine. Once the cleaner has had time to penetrate the grime on your engine, you can use a wire brush to scrub the aluminum parts of the car, but don't use this on plastic components. These parts need something a little more gentle - a hard-bristle brush can do the trick, and you can wipe away anything left over with soapy water and a sponge.
After you've thoroughly cleaned everything, you can rinse off the engine with regular water. Take care to wash all the soap away, and inspect the engine bay to make sure you haven't missed any spots. Once as much dirt as possible as been removed, let your car dry out completely. If you attempt to drive a car with a wet engine, you could get water in places it shouldn't be and damage some parts of the engine. This could take as little as an hour or two if it's especially hot or sunny, but you can let the car sit overnight just to be safe. When the engine is completely dry, you can remove all the plastic wrap and reconnect the battery cables.
The underside of the car needs to be cleaned as well, but this can be difficult to reach without a jack. If you don't want to lift your car up to hand-clean this part, you can always just shell out a few bucks at an automated car wash. These may have the ability to clean underneath the car as it rolls through the cleaner. You won't have to worry about washing the exterior either if you choose to go this route.