Establishing a solid preventive maintenance (PM) program is the key to getting the most productive use out of your truck and trailer.
“A good PM program means you are doing everything you can within reason to help keep your asset up and running all day, every day,” explained Darry Stuart, president of consulting firm DWS Fleet Management and a former fleet manager with decades of experience under his belt.
“For example, it’s better to pull and replace a tire early in order to prevent a road call and potentially scatter tire debris all over the road due to a blowout,” he said.
And that’s a situation any trucker wants to avoid, whether they operate just one tractor-trailer or a fleet of them.
“It is all about the cost of scheduled maintenance versus unscheduled maintenance,” he explained. “A good PM will take 2½ to 3½ hours to complete, especially with the emission control systems involved. What you care about is the quality and completeness of the PM, not the time.”
Homer Hogg, manager of technical development at TravelCenters of America (TA), is also a big believer in that same maintenance philosophy. Before his first stint at TA that began back in 1982, Hogg worked his way up from truck technician to master technician, then to director of maintenance training and quality control at a national trucking company. He returned to TA in 2010 and helped finish cementing together TA’s truck equipment service operations with that of fellow truck stop chain Petro Stopping Centers. (TA and Petro merged in 2007.)
“Truckers work hard to control their maintenance costs,” Hogg noted. “They are always looking for more efficient ways to maximize the life of every component on a truck while keeping the truck on the road as much as possible. Some technologies, such as telematics, are helpful, but there is no substitute for tried-and-true maintenance practices.”
Thus, despite all the many advances in connected vehicle technology in recent years—developments that in many ways have turned big rigs into nothing short of rolling computers—trucks still rely on mechanical processes to move, he stressed. And those “processes” require regular maintenance in order to operate effectively and with maximum efficiency.
From that perspective, then, both Stuart and Hogg compiled a list of maintenance basics that truck operators should pay close attention to in order to keep their rigs up and running and making money.
“You really need to bring clarity to the preventive maintenance process and to consistently take care of things on a truck that are absolutely critical, such as batteries, brakes, front axle alignment, tire air pressure, and the like,” Stuart explained.
“Also, PMs used to be scheduled around [engine] oil and [chassis] grease intervals, but that should not be the case anymore,” he noted. “The quality of oil and grease used to be the reason for PM schedules, but now their base quality is no longer really the issue. The real issue is the quality of the PM you perform in order to maximize vehicle uptime.”
In the same vein, here are Stuart’s top seven maintenance items:
- Batteries: At each PM, remove and clean the battery and connectors, then load test each one. “This is almost more important than checking the engine oil because if the truck doesn’t start, it won’t go,” said Stuart. “Buy a $100 battery tester and know how to use it. And at every PM, you check the battery; not once a year, not once before winter and summer—every time you conduct a PM. And when you put it back into place, don’t spray or grease it. You can’t tell what is clean and what is not. It’s hard to test if it’s covered in grease.”
- Pressure test the coolant system: “The majority of fleets I visit don’t ever do this,” he noted. “Yes, you may cause the system to fail, but you want it to fail in the shop, not on the road. Even more important is to check the EGR cooler at the first sign of a coolant leak. Also, [it’s important to note that] part of the pressure test is to check the cap because caps fail, and most people don’t realize how important caps are to the integrity of the cooling system. Pressure raises the boiling point of the coolant.”
- Check the brakes and brake stroke: “The stroke is critical: you need to inspect the brakes and check the stroke at each position,” Stuart pointed out. “You cannot rely on the original settings because automatic slack adjusters are the most abused part of the braking system. They wear out and fail. They are not ‘last forever’ components.” If you know you have a brake stroke issue, adjust it, fix it, or replace it. “Do it then in the shop; don’t have it fail a roadside inspection,” he emphasized.
- Check the front axle toe-in angle at every single PM: “This only takes five minutes. Usually, it gets checked after the steer tire wears out. If you are doing this correctly, you should not need to change tires in between PMs,” Stuart said.
- Add lubricant where needed: “There are very few manually greased parts of a truck anymore. It’s minimal, so PMs should really be scheduled around greasing intervals,” he said. “Engine oil is not the factor of vehicle life anymore; it’s the quality of the PM and the application of grease that is the issue, not the quality of the oil and grease. U-joints don’t fail due to the quality of the grease; it is the procedure. Kingpins and U-joints are your two weakpoints, but if you grease [components] properly you can run 50,000-mile intervals. We have a minimalnumber of places to grease now—and most don’t do as good a job as they should.”
- Check tire pressure at every PM: “I also like being consistent, so I run all OTR tires on a truck at 100 psi or 105 psi depending on the axle,” Stuart noted. “You should also check the weight rating of the tire.” He believes the tires should be swapped out when they reach 4/32nds or 5/32nds worth of tread depth. “Do not wait until 2/32nds or 3/32nds; the DOT minimum does not mean that is the optimum PM metric,” he said. “Who cares if you can get another 15,000 miles out of a tire if you fail a roadside inspection or the truck suffers a blowout and requires a road call?”
- Change both air and fuel filters: “Follow the air filter restriction metrics on the truck; if it can’t make it to the next PM, change it,” he noted. “The majority of fleets change it once a year, but the instructions say once a year or due to air flow restrictions.” Fuel filters should be changed at every PM, Stuart added. “Don’t try and get another 20,000 miles out of it and risk a road call.”
From where TA’s Hogg sits, there are five basic maintenance categories he believes truckers need to focus on that will help head off problems that can leave a truck stranded on the side of the road.
“Number one on my list is lubrication,” he said. “With extended engine oil drain intervals comes the tendency to align the chassis lubrication with the oil change. But this trend must be carefully evaluated.”
Certainly, he said, extended life components are available, but they are not a “silver bullet.” For example, some U-joints installed on a truck from the factory have no grease fittings and are designed to run several hundred thousand miles trouble-free. Yet Hogg said many of these U-joints will eventually need to have a grease fitting installed and a normal lubricant regimen added.
“I’ve seen many failures of these U-joints as a result of the grease fittings never getting installed, or the joints just failing as they reach the end of their lubrication life,” he explained. “Many truckers perform a ‘dry’ preventive maintenance check between their oil changes primarily designed to get the vehicle lubricated properly.”
Like Stuart, Hogg believes the engine cooling system needs special attention, and thus it ranks second on his list of five basic maintenance areas to monitor.
“About 50% of major engine failures are due to poor coolant system maintenance,” he explained. “At one time, the trucking industry was mostly concerned about the freeze point of the antifreeze and the metals protection provided by the additives. Those concerns are still relevant, but antifreeze has become much more complex.”
Modern engines contain a higher amount of “lighter metals,” such as aluminum, Hogg said, and such metals are not always receptive to some of the chemicals traditionally added to coolants. Thus, maintenance personnel must understand which coolant is required and keep track of the condition of that coolant.
Number three on his list are exhaust aftertreatment systems, for they are closely connected to the cooling system. That’s because if a truck is losing coolant but no external leak can be located, it may be escaping through the exhaust system and making its way to the aftertreatment system.
“If that is happening, major damage could be the result. The costs to replace a damaged diesel particulate filter (DPF), for example, could be several thousand dollars,” Hogg warned. “Technicians must use diligence to determine the root cause of any coolant loss and get the problem corrected before the truck suffers unscheduled downtime and costly aftertreatment repairs.”
In addition, cleaning DPF filters must be part of any trucker’s regular maintenance program, especially if they are planning on keeping their vehicle to and beyond the first required DPF cleaning cycle.
“We now move on to tires, which have always been a concern because of the costs to replace them and the many factors that cause excessive tread wear,” Hogg said.
Both Stuart and Hogg believe that maintaining proper air pressure is critical. “Matching the air pressure to the load is an important part of getting the most out of your tires—and the tire manufacturers publish charts to help determine the proper air pressure required based on the load,” Hogg emphasized.
He explained that a good way to remember some of the key areas to focus on relative to tires is to remember the acronym AIM, which stands for alignment, inflation and matching. Align the steer and drive tires, inflate your tires to match your load, and then match the height and design of the tire tread of each axle.
“Doing those three things [alignment, inflation and matching] will help you better control tire costs,” he said.
Finally, cranking and charging systems must be ready at all times, explained Hogg. “The good news is that these systems haven’t changed much in more than 40 years nor have the maintenance practices needed to keep them trouble-free.
“Yet I am still amazed at how many technicians across the trucking industry change batteries, alternators and starters and fail to check cables and connections,” he pointed out. “The majority of starter and alternator failures are a result of bad connections and corroded cables.”
You should test your cables and connections at least once or twice a year, Hogg added. “This discipline alone will begin to drive down your costs and drive up your uptime.”
The "1-10-100" Rule for PMs
Homer Hogg, manager of technical development at the TravelCenters of America chain of truck stops, swears by a unique maintenance philosophy he’s dubbed the “1-10-100” rule. By that he means if you can get your vehicle inspected at the correct interval and make the necessary repairs, you will be running your maintenance cost in the proverbial $1 range.
But if during the inspection the technician identifies repairs are necessary and those repairs are put off, a fleet now moves up the scale to the proverbial $10 range.
Unfortunately, if the vehicle breaks down because of a lack of maintenance or by not repairing an identified defect during the PM, a fleet is now operating in the proverbial $100 range.
“Fundamentally, this all means if you get your truck on the correct PM schedule and get it in on time, your maintenance cost is relatively low and controlled,” Hogg explained. “But if you defer any defects identified during the PM inspection, the cost to make the repair at a later date will be higher. If you defer long enough and the defect causes a breakdown, your maintenance costs will be exponentially higher.”
At its heart, he believes a good PM program is designed to apply an OEM’s maintenance rules to a truck or trailer along with identifying defects.
“Part of the value of a good PM program is to get the defects corrected while the vehicle is in for the inspection,” Hogg added. “Experience tells me that over 90% of all trucks receiving a PM will be found with defects that will need to be repaired or corrected.”