There is no doubt that preventive maintenance is the key to keeping buses road ready, reducing vehicle operating, maintenance and replacement costs and improving the bottom line.
Here are some of the areas often overlooked, as well as common mistakes made in bus fleet maintenance practices:
Leaks. Air cleaner elements should be changed based on intake restriction, not necessarily at regular intervals. In buses, the entire intake system should be inspected, including all flexible hoses and connections. Each time the air cleaner element is changed there is potential for dirt to enter the engine.
Premature changes often result in dirt entering the engine, and small amounts of dirt cause accelerated engine wear. In used oil analysis, dirt will show up as high silicon content.
Starting aids. If you use Ether as a starting aid, remember you are dealing with an explosive that can seriously damage your engine.
Never let a starting aid substitute for the correct viscosity oil. An engine that starts despite the sluggishness of the oil will receive almost no lubricant at critical points for several minutes after start-up. That is when significant engine wear can occur. Engines should operate at low idle until full and stable oil pressure is established.
During cold starts, the full flow oil filter bypass may open if the full flow oil filter restriction is high due to debris from long oil change intervals. When the oil filter bypass valve opens, often debris caught in the oil filter head is washed through the engine’s main bearings, causing bearing damage. Bearing failures result from severe dirt cuts, but often not immediately when the bearing damage is done.
During cold starts, long oil delays also have an adverse effect on such things as camshaft bushing and cam follower assemblies. Repeated long oil delays have an adverse effect on engine durability and component reliability.
For buses stored in outdoor depots in cold climates, lower viscosity oils may be needed.
Cooling system. Keep a close watch on your cooling system. Some experts believe that 50% of all premature engine failures begin with a problem in the cooling system. Check cooling fan belts for wear. An intermittent squeal often signals a loose belt.
Choose your antifreeze/coolants and supplemental coolant inhibitor wisely. Coolant leaks deplete not only antifreeze but also supplemental coolant inhibitor concentration. Manufacturers’ recommendations should be consulted at all times.
Coolant leaks into the engine oil may be found using oil analysis. Elevated levels of elements such as sodium, potassium, boron and silicon may indicate a coolant leak, as well as low coolant levels.
Fluid ratios. Less can be more. Don’t increase the ratio of antifreeze/coolant to water above 70:30, expecting that a “stronger” mix will do a better job. It won’t. For optimum freeze protection, always follow the manufacturer’s recommended ratios.
Turbocharger. If you’re using a turbocharger without a separate oil circulation system, let the engine idle a few minutes before shut down so the oil can cool down; otherwise it may “cook,” shortening its useful life and forming harmful deposits on the turbocharger bearings. Using a high quality engine oil with excellent detergency and antioxidants is also an important consideration.
Idling. If you’re concerned about fuel costs, try cutting down on your idling time. In most ambient conditions, engines will retain enough temperature to restart after sitting a few hours. Anything beyond idling for a few minutes after a long run wastes fuel, may reduce the life of your engine oil and promote corrosive wear in the liner and bearings.
Why? Because engine temperature is so much lower when you’re idling, and water vapor can condense in the crankcase and produce corrosive sulphurous acid. With the right choice of engine oil to help your cold weather starts, most of that idling can be avoided. Idling can also lead to high levels of soot in your oil, which can shorten oil life and thicken oil prematurely.
Additives. Supplementary additives (top treats)—even those sold under popular brand names—are an expense that you can live without. If you’ve made a good choice in engine oils, you don’t need any other products in your crankcase. In fact, supplemental additives may destabilize your engine oil.
Fluid levels. Maintain proper fluid levels. Running an engine while the oil level is too low can cause engine damage. Too high an oil level often results in rapid oil loss out the breather.
Fueling. Try to fill your fuel tank at the end of the day, rather than first thing in the morning. That helps prevent condensation from forming in the tank overnight; condensation often leads to a build-up of water and sludge.