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Diesel engines have become very popular in the grounds-maintenance equipment market. They are durable, fuel-efficient and provide the power you need to get the job done. However, these attributes do not come without a cost. The engine in these types of machines is the single-most expensive component in them. A diesel engine is more costly than a gasoline-powered engine of the same horsepower, so to protect and maximize your investment, proper engine maintenance is crucial. With proper engine maintenance, you will minimize down time and maximize the reliability and life of your engine.

Engine performance, reliability and durability depend on several factors, including fresh, clean fuel; clean air; proper lubrication; and appropriate engine temperature. In addition, there are operating practices that can significantly influence engine life. With every new machine the manufacture includes maintenance instructions. They develop these to guide you in caring for your machine so that you may realize maximum value from it. For optimum performance of your diesel engine, don't skimp on maintenance. Make sure that you are properly maintaining each of these elements.


To produce power, an engine obviously needs fuel. The fuel-delivery system in a diesel engine is precise and, consequently, very sensitive to dirt and contamination. For this reason, always fill your tank with fresh, clean fuel. The fuel system on your machine has at least one fuel filter and a water separator. You should change filters periodically and drain the water separator daily. You will need to inspect hoses and connections to assure there are no leaks. Remember to bleed any air from the system anytime you change a filter or open the system for any reason. If the filter or water separator fails to do its job, it will cause damage to the fuel-injection pump. A fuel-injection pump problem will cause downtime for you, and repairs are expensive.


Regularly maintain the air cleaner to ensure that clean air is being supplied to the combustion chamber. Your operator's manual provides instructions on regular and proper maintenance of the air cleaner on your machine. If you have an air-cleaner restriction indicator, it will tell you when to service the filter. If you operate in dustier conditions, you should check the air cleaner more frequently. Following these maintenance procedures will decrease the probability (or at least the frequency) that you will experience the two basic problems that can affect air cleaner: plugging or improper filtering.

An air filter collects dust that is in the air. As this happens, the filter will become increasingly restrictive, to the point of plugging. Symptoms of a plugged air filter are reduced engine power and excessive black exhaust smoke.

If a filter is damaged or not properly installed, dirty air will enter the combustion chamber. This dirty air will result in abrasion or wear of internal engine components, especially piston rings and cylinder walls. Symptoms of a “dusted” engine are excessive oil consumption, due to worn piston rings (blue smoke); low power; and difficult starting, due to decreased compression.

When you service the air cleaner, always inspect the filter for damage. Make sure all seals are in good condition and all hose clamps and other connections are tight. Remember to take a look in the hoses and the manifold area. If dust is present, you probably have an air cleaner problem that you should address immediately. You can clean a filter with low-pressure air by blowing the air from the inside of the filter or by gently tapping it on a firm surface. The air nozzle tip should be no closer than 2 inches from the element media, and you shouldn't use air pressure greater than 100 psi.

After cleaning, check the filter element with a light. If you can see any light through the paper filter media, it is damaged and you must replace it.


You should check the engine's oil level daily. When checking the oil level, observe the condition of the oil. If it has a milky appearance, there is likely water contamination. If the oil smells like fuel, there is likely fuel contamination. Both of these are indicators of engine problems.

Change the oil and filter as recommended in your operator's manual. Always use a high-quality oil with the recommended American Petroleum Institute (API) category and viscosity. The current diesel oil API categories are CF, CF-2, CF-4, CG-4 and CH-4. Any category not listed here is obsolete. But you can use one or more of the current categories in place of an obsolete category. Select the viscosity based on the ambient temperature. In cold weather, use lighter-weight oils, and in hot weather, use heavier-weight oils. Your operator's manual will provide a list of recommended oils that will likely include both straight-weight and multi-viscosity oils. Engine manufacturers have done extensive testing and know what oil will best protect the engine in your machine.

Used-engine-oil analysis can be a useful tool to monitor the condition of your engine. There are several labs across the country that offer this service. They will check for wear metals and let you know if excessive wear is occurring in your engine. They also will check for water and fuel contamination and report on the overall condition of the oil. This service may be especially useful if you are managing large fleets of equipment.


It's critical to maintain proper engine temperature. An engine will overheat if the coolant level is too low or if an inadequate amount of air is passing through the radiator.

Check the coolant level regularly. Inspect the radiator, hoses and all connections for leaks and repair any leakage before continuing to operate the machine.

Also check the coolant for freeze protection, contamination (engine oil) and visual appearance (determine if it's dirty or rusty looking). A 50/50 mixture of water and antifreeze will provide adequate freeze protection and also corrosion protection for the engine.

The radiator requires an adequate amount of air flowing through it to cool the engine. If the radiator fins are plugged with debris, the engine will overheat. So clean the radiator regularly. As with the air cleaner, the dustier the working conditions the more frequently you should clean the radiator. It is best to use compressed air to clean out the radiator fins. Do not use water because it will not remove all the debris and can cause settling of debris in the lower portions of the radiator core. Also, the water can react with some turf chemicals and damage the radiator.

If the fan belt or water-pump belt is slipping, the cooling system will not function properly. Regularly inspect the belt and check the adjustment. If it is cracked or worn, replace it before it fails. If you have an electric-powered fan, check to be sure that it is functioning properly.

To assure proper airflow, also keep the engine compartment clean. Many engines are enclosed within the vehicle frame and hood. Typically, air flows through the radiator and past the engine and then is exhausted out of the engine cavity. If there is excessive debris build-up on or around the engine, it will restrict airflow and compromise cooling.

Operating practices

For those of you who operate your machines in cold weather, you should take some precautions. As mentioned above, use the proper weight engine oil along with the appropriate grade of fuel. Using your “in season” locally available fuel should cause you no problems. Summer or No.-2 fuel will thicken or congeal at cold temperatures and will not flow in through the fuel system. No.-1 fuel or a winter blend will flow freely in cold temperatures. When starting, always use the preheat system (glow plugs) to assure that the engine starts quickly. If possible, store the machine in a heated area or use available engine heating methods.

A turbo-charged engine also requires special precautions. Turbo-chargers use the hot exhaust gases to power the turbo-charger and create rotation of the compressor on the intake side to force air into the combustion chamber. The turbo-charger will rotate over 100,000 rpm at full load. Its bearings are continuously lubricated as the engine runs. If the engine is shut down under load or at high speed, the turbo-charger will continue to run while receiving little or no lubrication. This will cause bearing and seal deterioration. It is a good practice to let the engine run at low idle for a short period of time before shutting it off. This will allow the turbo to slow down and not spin without lubrication.

Remember, machine maintenance is a series of regular and routine actions that require a plan. You have control over in how you treat your machine. If you treat it properly, you will minimize down time and will realize maximum value from your machine. Whether operating your machine or performing maintenance on it, make safety a priority. Always follow the safety instructions on the machine and in the operator's manual.

Steven A. Points, PE is the manager of product evaluation for the Commercial Products Division of The Toro Co. You can e-mail him at

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