The engine is often referred to as the heart of the machine and thus must be cared for accordingly. It is not unusual to find that engine oil and filter replacement intervals are adhered to only haphazardly. Many mechanics are unaware that when they change the engine oil, as well as oil and fuel filters, they must also check and replace the coolant filters and crankcase breathers at the required intervals.
Replace filters at the manufacturer’s recommended intervals. Also, remember to replace engine oils as specified for the application and grade.
Regular ‘off-the-shelf’ mil spec engine oils must be replaced after 250 hours of operation, and it is good practice to replace the engine oil filters every time and the fuel filters every other time the engine oil is changed. There are severe-duty (API CI-4 and ACEA E5-02) engine oils available on the market. The oil change intervals for these oils can be stretched to 500 hours of operation. However, because these oils are very expensive, customers shy away from using these oils but extend the oil change intervals far beyond the 250-hour mark even when using the less-expensive ‘off-the-shelf’ oils.
Vital machine systems
Service the cooling system. Most of today’s high-performance diesel engines feature a coolant filter and require a specific DCA4 additive concentration in the coolant fluid. This additive builds up a protective coating in the entire cooling system that is important to avoid cavitations around the liner walls.
If such coating is missing, material starts to erode from the outer surface of the cylinder liner wall that is surrounded by the streaming coolant fluid. Such erosion can result in the development of pinholes through the entire liner wall.
Engine failures are imminent when coolant and antifreeze enter and dilute the engine oil. Therefore, coolant fluid must be checked every 500 hours to ensure that the prescribed DCA4 additive level is maintained.
Maintain the crankcase breather assembly. Another shortcoming is servicing the crankcase breather assembly, which filters hot gases escaping from the crankcase. The filter insert, that is part of the breather assembly, separates the residual oil from the gases and returns it to the oil pan. The filtered gases are recycled through the combustion air intake system of the engine. If this filter insert is soaked with oil and/or plugged with solid particles, or the crankcase breather housing is dented, the suction of the turbocharger will actually attempt to siphon engine oil out of the crankcase. Many mechanics mistake the developing smoke as a consequence of a failing turbo charger.
Also, if a malfunctioning crankcase breather is not replaced in time, the entire combustion air system will be coated with oil residue that may cause the after-cooler to become less effective, a problem that can over time cause the engine to overheat.
Watch your step when servicing machines. Maintenance personnel sometimes do not pay attention to what they step on when servicing a machine. Stepping on fuel and/or electrical lines must be avoided at all times.
Damaged fuel lines may develop leaks and electric lines may cause shorts, both potential fire hazards, especially when the machine is not cleaned on a regular basis.
Check the air cleaner daily. Operators should check the air cleaner indicator daily. Often, the indicator sight glass is not visible because it is completely covered with dirt and/or oil residue. Plugged-up air filter elements will cause the turbo charger to suck the air out of the crankcase, or the engine’s fuel injection system may try to compensate for the lack of air with an increase in fuel injection, which in turn, will cause the engine to overheat and eventually fail.
To keep the engine healthy and productive for a long time, the air cleaner must be checked daily and the filter elements changed at the manufacturer’s recommended exchange intervals.
Use clean fuel and check injectors.
It is recommended to check and replace fuel injectors every 3000 hours of operation to avoid worn out and dripping injector nozzles, which can cause over-fueling and piston crown meltdown.
Hydraulic system maintenance
Today’s hydraulic systems are self-contained and need little maintenance with the exception of an occasional filter change and hydraulic fluid replacement.
Replace fluid and filters at the manufacturer’s recommended intervals
Replacing the hydraulic fluid and filters at the required intervals is the best prevention to avoid premature failure and expensive component repair.
Owners and operators are best served when they additionally monitor the hydraulic fluid by taking frequent oil samples. Then again, oil samples must be taken carefully and the oil analysis reports must be properly interpreted to be of value as a maintenance tool.
Also, it is good practice to fill and bleed hydraulic pumps or motors after replacement to prevent a dry run, which can destroy the component minutes after installation. This pre-filling procedure is especially important if a hydraulic component is installed above the hydraulic fluid level in the tank.
Use proper viscosity fluid. Another problem that occasionally crops up is that customers do not always use the quality oils and viscosity grade recommended by original equipment manufacturers (OEMs). Hydraulic fluid with too low of a viscosity will cause excessive internal wear and lead to overheating that will harden and destroy seals and hydraulic hoses. As a result, the machine will start to leak and lose efficiency.
General machine maintenance
Follow precautions when adding electrical components.
Jobsite conditions frequently require the installation of auxiliary electrical or electronic equipment, such as additional working lights or DC to AC converters that require high amperage.
Many times, such accessories are connected without checking the available maximum alternator output on the machine. For example, an excavator may be equipped with a 50-amp alternator; therefore, the maximum current draw of all electrical appliances combined must remain below the maximum alternator output.
Also, power supply (hot) wires are often spliced into what appears to be a hot wire or connected to a hot terminal.
Electrical problems are often the direct result of such unprofessional installations. There is no reason to make such connections as most manufacturers make provisions for electrical accessories.
Visually inspect the machine on a regular basis
Most machine or component failures could be completely avoided with a few preventive machine inspections. Structural cracks particularly can be detected most of the time in their initial stages at a time when corrective repairs and reinforcements are still possible.
Many customers do not bother to initiate a preventive maintenance program that includes steam cleaning the entire machine at reasonable intervals and performing thorough visual inspections of all structures, especially attachments.
For instance, when inspecting a fracture, a trained engineer can see whether the fracture occurred suddenly or developed throughout a period of time.
Strictly follow the OEM’s recommendations. It should be company policy for each mechanic to read the safety and maintenance sections in the operation and maintenance manual, supplied with each unit.
Participate in annual maintenance training
Establish a machine cleaning and inspection schedule that must be documented and adhered to. If severe, deficiencies should be corrected immediately, or if they can wait, deficiencies should be corrected during the next machine service.
Make the operator part of the maintenance team. A good operator should make a walk-around inspection prior to each shift.
On one hand, most equipment manufacturers design their machines as user friendly as possible. On the other hand, they are forced to make their machines more efficient and productive. Because the later requirements are accomplished by integrating electronics and microprocessors, these machines have, throughout time, become more and more sophisticated and require a new maintenance approach. The service mechanic of today has to learn to use sophisticated electronic equipment and a laptop computer. Proper maintenance will ensure not only safe operation, but extended service life.
Wilfried Wotke is general manager of product support for Liebherr Construction Equipment. He holds a master’s degree in mechanical engineering and has been involved in product development and support with Liebherr for more than 35 years.