Warning signs of hauling truck engine failure include strange noises (like knocking, grinding, or squealing), dashboard warning lights (such as check engine or oil pressure warnings), and reduced power. According to the National Institute for Automotive Service Excellence, 30% of engine failures are detected early through these symptoms, saving 20-40% in repair costs when addressed promptly.

Strange Noises

Haul truck experience is nearly fifteen years for me, and one thing I am sure of: strange noises signal engine failure is afoot or underway. Data notwithstanding, the study from the National Institute for Automotive Service Excellence (ASE) in 2022 puts in excess of 30 percent of engine failures down to strange noises. That’s not an insignificant amount, and if you’ve been around trucks long enough, you’ll appreciate that those noises can signify the proverbial first faint signs of something sinister going wrong.

Knocking noises are a simple example. This common diesel engine problem could indicate anything ranging from low oil pressure to a damaged crankshaft. According to engine repair cost data, ignoring knocking sounds could create a repair bill somewhere between $2,000 and $8,000, depending on how much damage is done. Last year, a truck of mine was slightly knocking, and that was ignored for months. When it was finally worked on, it cost $4,500 and kept the truck off the road for almost a week. If this had been done sooner, it would have been cheaper because it has appropriately indicated to you now how much money you are going to lose when you ignore your engine.

Then there's the grinding sound, which never ever sounds good. Grinding on acceleration or shifting usually means more than a worn-out part. A TEPI analysis of truck engine operation determines that grinding sounds are most typically caused by worn gear elements, incorrectly adjusted clutches, or worst-case transmission component damage. In the event that you do determine that there is a grinding sound emanating from the transmission, then the repairs can range from $1,500 to $3,500 based on the issue, with labor typically exceeding $150 per hour in upscale metropolitan areas. A friend of mine had a grinding sound in his hauling truck, and when he had it checked, the gearbox needed to be replaced. That was 4 days and $2,800 by itself—and that doesn't even account for lost time.

Another sound that should not be ignored is high-pitched squealing sounds. Squealing is usually caused by wear or misalignment on belts or pulleys. An American Trucking Association (ATA) analysis identified that 20% of recent roadside breakdowns were caused by bad belts. Specifically, a truck's serpentine belt, which drives multiple engine accessories, can lose tension as it wears or becomes frayed. A worn serpentine belt may cost $200 to $500 in parts and labor to replace and needs to be replaced every 60,000 to 100,000 miles, depending on use and environmental factors. Example: a truck that a friend owned began squeaking at around 80,000 miles. Not maintaining it made the alternator almost entirely burn out, which cost him an additional $1,200.

That rumbling sound that you occasionally hear? You'd think that's normal, right? I mean, trucks are big, heavy-duty vehicles, so they're going to rumble. But when the rumble gets louder or becomes a roar, that can mean catastrophic damage. Rumbling noises from the exhaust or engine, such as those reported in a 2020 article in Fleet Maintenance, are symptomatic of cracked cylinder heads or ruined pistons. These problems are extremely costly to repair, even reaching over $10,000 for an engine rebuild in some cases. I have personal experience with this—A truck I once worked on had a rumble that would only get louder and louder until it was simply a roar. By the time we tore it apart, the pistons were completely blown. It took around 10 days to repair, and the truck owner had to shell out $8,500.

Power Loss

Truck power loss during hauls is one of the most common and frustrating issues fleet owners face, and it can be triggered by a multitude of culprits. The American Trucking Association (ATA) says that about 18% of fleet breakdowns can be traced to a loss of engine power, costing the industry $6 billion annually in repairs and productivity losses. Issues with the fuel system are one of the leading causes of power loss. In fact, fuel injectors, if they are clogged or malfunctioning, can result in a 15-25% decrease in engine power. A friend of mine had an old truck with injector problems, and after getting them cleaned, the truck regained 20% more power—not only improving fuel efficiency but also increasing its speed by about 10 miles per hour on the highway.

Another key factor contributing to power loss is air intake restrictions. The EPA estimated that a clogged air filter can decrease engine efficiency by up to 10%. It does not seem like much at first, but if you calculate that an average haul truck uses 50-100 gallons of fuel per day, a 10% efficiency loss can be an extra $100 to $200 per week in fuel costs. One of my fellow workers neglected to change his air filters on a truck for almost 90 days, and it not only resulted in a noticeable loss of power but also in fuel economy—a surprise fuel bill of $1,800 more in a single month.

And don't forget the exhaust systems, in particular the Diesel Particulate Filter (DPF). When the DPF is clogged—often due to improper or infrequent maintenance—engines lose power dramatically. In research completed by the Society of Automotive Engineers (SAE), it was found that up to 30% of diesel engine power can be lost when the DPF is not cleaned or replaced on a regular basis. DPF regeneration cycles can be a nightmare for truck drivers because, during the process, they can notice a dramatic decrease in engine power, as much as 40% in certain instances. The performance decrease would undoubtedly cause delays, affecting delivery schedules and, ultimately, customer satisfaction. One of my trucks went through a regeneration cycle that took two hours, during which the engine power reduced so drastically that it could not even maintain highway speeds. The owner had to pay an additional $1,500 for an emergency clean-up job just to get the truck back to full operation.

Power loss can also be caused by fuel contamination, and the National Institute of Diesel Mechanics (NIDM) states that as little as 5% water contamination of fuel can cause up to a 15% loss of the engine's power output. This is particularly a risk to fleets that travel around where fuel quality is inconsistent. Water in fuel dilutes the combustion process, resulting in poor engine performance and wear on major components. I recall an instance when a truck lost power drastically, and when the fuel was tested, it had nearly 8% water. The truck owner had to drain the tank and replace the fuel filter, which came to $800 for the service alone, not to mention downtime and productivity loss.

Another factor is motor oil, which directly affects power performance. Dirty or old oil causes the engine to work harder than necessary and results in a power loss. According to an Engine Manufacturers Association (EMA) study, dirty oil can reduce engine performance by as much as 12%. While an oil change might be a simple fix, when trucks are running upwards of 1,000 miles per week, letting oil go bad over time can amount to a significant performance decrease. I’ve seen trucks with over 150,000 miles that were running on oil that hadn’t been changed in more than 10,000 miles, and the result was a noticeable 15-20% loss in engine power, costing the owners $500 to $1,000 in repairs once the oil was replaced, not to mention the prolonged wear on other engine parts.

Warning Lights

When those caution lights start flickering on the dashboard of your truck, they're not just a nuisance on your neck—they're often the first sign that something serious is wrong. A study by the Federal Motor Carrier Safety Administration (FMCSA) indicates that nearly 40% of breakdowns on the roadside are the result of mechanical failure, a lot of which would have been prevented if those warning lights were addressed earlier. Perhaps the most common of these is the check engine light, which, as reported by Fleet Management Weekly, accounts for 15-20% of all truck repair incidents. A J.D. Power study in 2023 found that over 60% of truck drivers ignore warning lights as minor issues, but this can lead to much more costly repairs. A run-of-the-mill check engine light, for instance, could be anything from a loose gas cap to an engine misfire of catastrophic proportions. If neglected, the fix will be $200 to $3,000, depending on the severity.

One of the most critical lights to pay attention to is the oil pressure light. Low oil pressure, a 2021 Truck Engine Maintenance Report found, is the reason for nearly 10% of commercial truck engine failure, with the repair cost of a failed engine averaging as much as $12,000. A colleague once experienced a loss of oil pressure when transporting on mountain routes, and this had prompted a warning light on his dashboard. When he let it slide without dealing with it for 48 hours, his engine totally seized up, and it cost him $10,500 to fix. If he had proceeded and checked when the issue started, he would have saved 70%.

Next is the battery's warning light, something that most drivers overlook thinking that it's bad. However, according to Car and Driver, bad batteries are one of the top causes of electrical truck breakdowns. Weak alternator or a faulty battery may lead to 25-35% power loss efficiency, draining the energy of your vehicle and having your car sit idle. My fleet that I operated last year included a truck with a persistent battery warning light. A week of not heeding it led to total electrical failure. Repair cost, including alternator and wiring replacement, totaled $2,200. The truck was also out of commission for four days, and that caused enormous losses of delivery time.

Brake warning lights don't ignore themselves either. The National Highway Traffic Safety Administration (NHTSA) estimates that brake issues are nearly 20% of all truck accidents. When the brake warning light appears, it is most likely due to low brake fluid, worn-out pads, or a faulty system. A report by Safety Research & Strategies found that cars with brake issues are 40% more likely to be in an accident. One of the trucks I fixed had a brake light on for days, and while we were able to fix it before anything went wrong, it cost us $800 in fluid replacement and pad checks. Had the ABS problem gone further, the likelihood of higher cost and much worse consequences would have been substantial.

The ABS (Anti-lock Braking System) warning light is another warning light to take note of. The warning is normally related to issues with the ABS pump or brake sensors that may impair your capacity to brake safely in some situations. A 2022 study conducted by Automotive Fleet found that 15% of total winter commercial truck breakdowns are ABS-related. Ignoring this light will result in further damage, and repair costs between $1,000 and $5,000 depending on the issue. The ABS system failed on one of the trucks in our fleet, and the breakdown to fix it cost $3,000. Aside from this, there was three-day downtime, with the truck no longer having its on-time delivery capability, negatively affecting our customer contracts.