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Rollin Along

Originally Published in MotorHome Magazine

Keeping a motorhome cruising past repair centers requires specific service procedures at prescribed intervals


For many owners, engine service means changing the lubricating fluids, but there’s much more to consider in order to keep a motorhome on the road without hiccups – and potential unscheduled service visits. Filter inspections should be performed regularly and in many cases coolant, for example, is usually out of sight, out of mind until the engine overheats. Servicing these areas is not difficult, but precise recommended procedures and parts selection must be observed for optimum results. The following is a continuation of last month’s article “Get Ready to Roll” on motorhome engine/drivetrain maintenance.

Cooling Systems

Cooling systems are comprised of the coolant, radiator, the upper and lower hoses, and the filter in diesel engines all functioning in harmony by way of the water pump that distributes the coolant. Heavy-duty diesel and gasoline engines have very different requirements for coolant. Monitoring the motorhome’s engine cooling system is often overlooked and when the mercury takes a jump to either an extreme high or low, the effects can be devastating. The boiling point of the coolant can lower to dangerous levels that can cause overheating and the freeze point can rise as well causing major damage such as a cracked engine block.
Even more critical to today’s modern engines are the supplemental coolant additives (SCAs) used in diesel engine cooling systems that protect against scale, corrosion and pitting, and keep cylinder sleeves from wearing out prematurely. Remember that all SCAs wear out at some point, making it critical to test the SCAs and freeze point of your engine’s coolant according to the specific maintenance schedule listed in the owner’s manual. Coolant test strips are available for purchase, but are not very accurate. Due to the fact that coolant and additives are so complex, multiple tests should be preformed and diagnosed by a professional technician. Modern diesel engines include filters as part of the cooling systems that eliminate abrasive materials, debris and other contaminates that may work their way into the coolant system. Filters must be changed in accordance with the recommended intervals specified by the engine manufacturer. Rarely do gasoline engines include OEM coolant filters.
Testing the radiator cap is another very important maintenance item that when overlooked can cause dangerously low pressure within the cooling system that will result in overheating. Radiator caps can be tested for the recommended pressure at a local radiator shop or you can purchase a tester at a local auto parts store or on the Internet. Radiator caps should be replaced from time to time due to the extreme temperatures and harsh chemicals that make up their environment. When replacing the radiator cap, double check to make sure the pressure rating is correct for the engine.
[nggallery id=4]Over time, all of the fluids in a motor-home engine’s cooling system reach the end of their life and will need to be flushed out and replaced to ensure maximum cooling efficiency. During the flushing process, excess scale, rust and other foreign particles will be removed from the radiator, water pump and the engine cavities. Time schedules on this necessary servicing will vary greatly so be sure to consult the owner’s manual for specific needs.
During the flushing process, have the upper and lower radiator hoses checked. Rotted, worn, collapsed or swollen hoses are the culprits of frequent cooling system problems, especially as the coach begins to age.
In the 1970s and ’80s, motorhome antifreeze was primarily comprised of a green colored ethylene glycol. Today, modern coolants are made up of different substances that come in various colored liquids and cannot be mixed together. Again, consult the owner’s manual to ensure proper selection and use of the coolant for your specific motorhome engine.

Air Filtration

Modern engines are being built with tight tolerances. Whether a gas or diesel, even a small amount of dirt can be fatal to a motorhome engine or turbocharger. Gas engines typically use a much smaller paper element filter than diesel engines that require a larger paper element or a sealed filter encased in metal. Motorhome diesel engines require more air simply because they are much larger than gasoline engines. Replacement intervals are similar despite their size difference. Diesel air filters have an overflow restriction gauge (aka, filter minder) designed to take the guesswork out of replacement intervals.
The filter gauge uses vacuum to determine filter condition. When dirt builds up on the filter, engine vacuum builds up between the filter and the engine, thus activating the minder. If you are in doubt whether the gauge is working properly, it can be reset by pushing the yellow button that is usually located at the bottom of the gauge and recheck the gauge after driving 20-30 miles. Keep in mind that you may need to check the minder and/or service the filter more frequently when in extra dusty and dirty conditions. Log driving conditions while continually monitoring the filter gauge, and of course inspecting the filter element. Replace the filter after two or three years regardless of mileage.

Tires and Wheels

The tires’ primary job is to carry the weight of the coach. With proper care they will last for several years (depending on mileage). Tires fail for many reasons; low air pressure, road hazards and age are among the most common. Motorhome tires typically do not wear out, as the majority of motor-homes are simply not driven enough to accumulate the number of miles to wear down the tread to unsafe levels. That being said, most motorhome tires time out due to sunlight, smog and other environmental effects.
The average lifespan of a motorhome tire is roughly seven years, although some manufacturers have specific recommendations. Every tire has a date code and being aware of the exact age of the tires is critical. Look for the D.O.T. letters and numbers on the sidewall of the tire. The last four numbers are the week and year the tire was manufactured; for instance 0608 would be the sixth week of 2008. It is far better to replace old tires when you’re at home than in the middle of nowhere, paying an exorbitant price on a mediocre tire while footing the bill for the tow truck. Check the air pressure in all tires, including the spare, before each trip and inspect the tires for cracks and damage.
Some tire specialists recommend filling the tires with nitrogen as a means to prolong the service life. Nitrogen is an inert gas that contains no moisture; it is used in place of compressed air and some experts feel it can extend the life of the tires, especially if it has been used from the day the tires were installed. The benefits of nitrogen may be small, but may be worth it in the long run, especially since the cost is not that high.
It’s highly recommended to use a tire pressure monitor system (TPMS) to warn drivers of a drop in tire pressure. Some TPMS systems will give a specific tire temperature reading within each individual tire. This is critical information since excess heat can cause high-pressure readings and could warn drivers of an impending tire failure. This is important because blow-outs not only destroy the tire, but cause collateral damage that is usually very expensive to repair. Knowing the exact weight on each tire allows the owner to determine the minimum air pressure needed for front and rear tires using the tire manufacturer’s load/inflation tables.

Fuel Filters

Most auto parts stores carry a number of antifreeze products, cleaners and additives.

Most auto parts stores carry a number of antifreeze products, cleaners and additives.

Until a problem arises, fuel filters are often overlooked as part of the routine chassis maintenance schedule. Usually, plugged filters rear their ugly heads when out on the road at the most inconvenient time or place. Diesel engine fuel systems are more finicky than gasoline engines and these systems have at least two filters, a primary and secondary, as well as a water separator. Many systems drain the water automatically but some require periodic manual draining. Some motor-homes have a warning light in the dashboard to indicate when water in the separator is at a critical level and in need of draining. Gasoline engines typically have one fuel filter and do not have a water separator. Check the owner’s manual for service intervals and the type of filter needed for replacement. Don’t skimp on price here; the better filters provide more reliable service.
Fuel filters are not difficult to change if you don’t mind getting a little fuel on your hands. Use a drain pan and follow the instructions in the owner’s manual. The process of changing diesel fuel filters is a little more complicated because it’s critical to prevent air from entering into the fuel system, which can create an injector problem. Filling the new filters with diesel fuel before installing them will make it easier to purge the system of air. Follow the instructions in the owner’s manual for purging the system carefully. It’s best to perform the procedure twice, to ensure that all the air is purged from the lines and filters.

Consult your owner’s manual to ensure the correct fluids are used for your engine’s cooling system.

Consult your owner’s manual to ensure the correct fluids are used for your engine’s cooling system.

Regular motorhome chassis maintenance will ensure better performance and mileage for years to come. Having a better overall understanding of how each system operates will provide the insight needed to determine whether the service procedure can be performed by you, and to be comfortable communicating with RV service technicians. Keep precise written records to prove that maintenance procedures were followed in case a warranty claim requires scheduled service.



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