Give your motorhome’s power plant a much-deserved cleaning so that not only will it look better, but also will run cooler and reveal potential problems more clearly.
By Bill Hendrix, F761s
October 2010
We owned our 1995 motorhome for several years before it began showing its age in the engine compartment. I had always polished the exterior, including the wheels, on a fairly regular basis but tended to neglect the parts not readily visible. Opening the engine compartment door on the diesel pusher revealed some oil and dirt accumulation, faded paint, and rusty areas. So, I decided to attack the problem with the goal that when I was finished with the job, the engine would appear much like factory new. This meant that simply painting everything one color, directly over top of the dirt and grime, wouldn’t make it right. If you would like to give your engine compartment a just-like-new appearance, here are some of the steps I took and some suggestions for cleaning and brightening this neglected area.
The first step when doing any type of engine refinishing project is to clean all oil and grease from the engine and accessory surfaces (including the inner fenders on Type C motorhomes). Before you begin the cleaning phase of this project, let the engine and manifold cool, as you don’t want to spray cold water on a hot engine and a hot manifold. A warm engine with a cool exhaust manifold is best.
Your best cleaning option would be to find a truck wash bay with a high-pressure sprayer using hot, soapy water. Such a facility may not be easy to find, but I would drive several miles for the service. One advantage to using a truck wash bay is that you don’t have to deal with any ecological issues related to the resulting runoff. However, if you have only a minor amount of oil residue to deal with and an acceptable place to do the cleaning, several cleaning products formulated for this purpose are available at auto supply stores. Read the labels, heed the warnings, and make sure the product is water-soluble for easy cleanup. If you have a pressure washer, use it in moderation with the above precautions. Many engine cleaners will work on a warm engine with just the pressure of a water hose spray for cleanup. The fins and cores on the radiator are delicate and can be damaged by the hard spray of a pressure washer, so rinsing this area with the softer flow of a water hose would be a safer method of cleaning. While you are washing the inside of the engine compartment, don’t overlook the wheel wells.
For Type A and Type B coaches, the firewall and the fender liners may be cleaned in the same manner as the engine block. These areas are not inclined to rust, and a good cleaning normally will suffice. If oil and grime persists, allow the cleaner some time to soak in and penetrate, and then repeat the process. Take care to avoid or make sure to cover any water-sensitive equipment, such as electrical connectors on the engine control module and the voltage regulator. Plastic bags secured with tape work well for fuse boxes and other small electrical items. If your motorhome has a gasoline engine, you should protect the distributor, carburetor, and air cleaner with plastic. Pay attention to the area below the shaft seals, as you’ll often find some oil dribble there.
Remember, safety first. Wear a face shield or goggles; long sleeves; a cap; and a pair of furniture refinishing gloves, which will give your hands the needed protection. Often there will be areas that need some hand scrubbing with an old toothbrush, steel wool, or wire brush to reach into corners and crannies that are a bit stubborn. If some of the oil residue has been baked into a varnish-like film, try using parts-cleaning solvent applied with a rag. Rust can be removed using a small wire brush or some emery cloth. After getting everything clean, let the engine and accessories dry thoroughly before beginning the detail work.
The trick to achieving a professional-looking paint job is to avoid overspray; to paint only the individual parts; and to restore them to their original color, or at least a color very close to the original. The engine block itself will have a distinctive paint that may be difficult to match unless you go to one of the engine manufacturer’s service shops and purchase the real stuff. Unless your engine has a rust problem, this shouldn’t be necessary, as the original paint used on engine blocks is typically very durable, and cleanup normally will bring it back to its original appearance.
To paint the accessories, gather some old rags, newspaper, and blue masking tape. Also purchase two or three small disposable paintbrushes and a variety of spray paints that are the appropriate colors to bring items back to near-original appearance. Several very good spray paints are available. Over the years I have had excellent results with Krylon and Rust-Oleum brands for a wide variety of paint projects. Rattle-can spray paint is best when used at temperatures of 70 degrees Fahrenheit and above.
After you have cleaned the engine block, focus on one accessory at a time. To help ensure paint adhesion, first lightly sand the surface with 220-grit sandpaper. While sanding, wear a dust mask. Cover all the adjacent surfaces and areas below with rags and newspaper, and carefully mask the paint line. If the masking tape won’t stick, the surface probably still has oily residue on it that needs to be removed.
Start by shaking the can for at least 2 minutes and continue to shake it frequently during the painting process. Spray the accessory with two or three light coats, allowing adequate drying time between each coat. Usually the bolt heads are black or some other color that differs from that used for the accessories. I prefer to paint over the bolt heads while spraying “” masking them off is pretty tedious “” then, after the paint has totally dried, paint the bolt heads individually with a small paintbrush.
Allow the paint to dry and then remove the rags and masking tape. There may be a spot or two that needs touching up. This can be done with a small paintbrush. Using a piece of cardboard to catch the overspray, hold the paintbrush 2 or 3 inches away from the spray can nozzle. A short blast will load the paintbrush bristles with paint. Then, touch up any areas, repeating with more paint if necessary.
Go to the next accessory and repeat the masking process once the previous paint is dry. Most rattle-can paint will dry to the touch in 10 to 15 minutes after the final coat. The pulleys don’t have much surface area and masking is difficult, so I use the paintbrush technique on them. Cleaning and brightening the belts, hoses, and other flexible lines adds a finishing touch.
Depending on the state of your motorhome’s engine compartment, this may be an all-day project or it could take up to a week. But once completed, you will have a cleaner, brighter, cooler-running engine, and you will be proud to open the compartment door.