Heavy-duty trucks must travel hundreds of thousands of miles on varying road conditions, so they come with durable engines. But occasionally, they encounter problems that can impact vehicle efficiency, performance, and overall reliability.
With regular maintenance, timely diagnostics, and training drivers how to identify common engine problems, fleets can cut costs from major repairs and avoid downtime.
10 Common Heavy-Duty Truck Engine Problems
Truck operators may be familiar with common breakdowns, but drivers can act quickly to prevent mechanical failure by learning to recognize common semi-truck engine problems. Quick thinking and reporting ensure that these heavy-duty vehicles stay safe on the road.
1. Engine Overheating
An overheating engine is a common, potentially serious problem in heavy-duty trucks. There are many factors that contribute to this, including cooling system issues, faulty radiator fans, a clogged radiator and a malfunctioning thermostat. Excessive load or towing beyond a truck’s capacity puts excessive strain on the engine. The engine must generate more heat than the cooling system can dissipate, causing an imbalance.
Look out for these signs of overheating:
- Steam or smoke: Visible steam or smoke from the engine compartment points to overheating. Sometimes this comes with a sweet odor, indicating a coolant leak.
- Temperature gauge warning: Drivers can identify a problem with the engine overheating by watching the temperature gauge. If it consistently exceeds normal levels, there may be a problem with the water pump, radiator or thermostat.
Regularly monitoring coolant levels, addressing belt or water pump issues and inspecting the radiator and fans alongside maintenance can help mitigate engine temperature problems. If the engine overheats, drivers should pull over immediately, switch the ignition off and contact their fleet manager.
2. Fuel System Issues
Malfunctioning fuel injectors lead to poor fuel atomization, which affects combustion efficiency. It also leads to power reduction, rough idling, and an increase in fuel consumption.
Fundamental problems with the fuel system include:
- Clogged injectors: Fuel injectors often accumulate deposits over time, which leads to clogging that disrupts the spray pattern.
- Injector pump failure: The injector pump pressurizes and delivers fuel to the injectors. If the pump fails, fuel distributes unevenly and the engine will encounter performance problems.
- Fuel contamination: If contaminants like dirt, debris, or water enter the fuel system, it compromises fuel quality and can damage fuel system components.
Air in the fuel system: Air in the fuel system is often the result of a fuel line leak or faulty seals — this disrupts proper combustion and increases emissions. - Fuel temperature issues: Variations in fuel temperature affect its viscosity and combustion efficiency. In extreme temperatures, this can lead to gelling or vaporization.
- Incorrect fuel injection timing: Issues with the injection pump or sensors lead to wrong fuel injection timing.
3. Emission Control System Malfunctions
The check engine light will come on when this system malfunctions. Malfunctions in the emission control system become more common with the increasing focus on environmental standards. The system consists of the exhaust gas recirculation (EGR) system, the diesel particulate filter (DPF), and the selective catalyst reduction (SCR) system with other sensors that help reduce harmful pollutants the truck emits.
Clogged DPFs lower exhaust flow and power and lead to engine derating if the filter is not replaced or maintained promptly. The SCR system uses diesel exhaust fluid to reduce nitrogen oxide emissions. Problems with this system can increase NOx levels, which will cause the truck to fail emissions tests.
4. Electrical Issues
In modern trucks, malfunctioning sensors affect the crankshaft, oxygen and coolant temperature. It can trigger incorrect data readings, which cause rough idling, engine misfires, and poor fuel efficiency. Issues with the alternator or starter can cause the electrical system to fail. This creates difficulties starting the engine, which can leave drivers stranded. Critical problems drivers may encounter are:
- Battery failure: Dead or weak batteries result from age, faulty charging systems, or electrical drains when the engine is off. They can cause temporary electrical failure.
- Starter motor problems: The truck’s engine does not crank properly when the starter motor presents issues.
- Faulty alternators: The alternators charge the vehicle’s battery, providing electrical systems with power.
- Problems with wiring and connectors: These components are subject to corrosion, wear and tear. Damage can cause electrical shorts with intermittent issues to the truck’s electrical system.
- A faulty ignition switch: Issues starting the truck, stalling, or failing to engage the starter can come from a defective ignition switch and lead to unexpected breakdowns.
- Fuse and relay failure: Faulty relays and blown fuses disrupt electricity flow, which can cause specific functions like wipers or lights to lose power.
- Sensor malfunction: When sensors like those working with the engine control module (ECM) produce incorrect data readings. It also affects emissions, engine performance, and fuel efficiency.
- Grounding issues: Corroded ground connectors cause electrical malfunctions due to poor conductivity. It is essential to inspect and clean these components regularly.
- Electrical system overload: Adding aftermarket accessories without consulting technicians with proper consideration for the truck’s capacity overloads the system. The overload causes electrical failure and potential damage to the truck.
- Trailer wiring problems: Trucks towing trailers need additional electrical wiring to use turn signals, brake lights, and other safety features. Ensuring these wires are in working condition is crucial.
- Instrument cluster malfunctions: If the instrument cluster – which includes warning lights – malfunctions, drivers see inaccurate readings. This stops operators from monitoring essential vehicle parameters on the road.
5. Exhaust Gas Recirculation Valve Failures
When the EGR system experiences problems like clogging or malfunctioning components, you will see an emissions increase, lower fuel efficiency and potential engine damage. Failure in the EGR is often a result of mechanical malfunctions or carbon buildup. Carbon deposits accumulate in the valve and its components, which prevents it from functioning optimally. The EGR valve can experience mechanical failure when the valve or solenoid gets stuck and disrupts proper functioning.
Diagnosing can be challenging as the symptoms often overlap with other engine problems. This means that correctly identifying this failure requires professional diagnostic tools and expertise.
6. Turbocharger Problems
Turbo lag, complete failure, or a reduction in boost leads to lower fuel efficiency. It can also cause potential damage to other engine components and a decrease in engine power. There are a few reasons why turbochargers may fail:
- Oil contamination: A poor-quality oil filter can allow foreign particles to lodge in the turbocharger.
- Bearing failure: Bearings can wear out over time because of high operating temperatures and poor lubrication. It causes an increase in shaft play and can break the turbo.
- Oil starvation: When the engine lacks proper lubrication, the engine and turbocharger can experience catastrophic damage.
- Restriction of airflow: Boost leaks and airflow restrictions usually come up with new turbocharger fittings. It often results from poor-fitting CAC hoses and piping or clamp failure.
- Engine wear: Consistent high speeds and temperatures can take a toll on a truck’s turbo, causing it to seize or become unresponsive.
- Foreign objects: Debris from CAC piping or hose damage can wreak havoc on a turbo’s impaler blades.
- Wastegate sticking: A sticking wastegate controls the amount of gas directed to the turbo and causes improper boost control. Along with overheating and performance issues, this can damage the turbocharger over time.
7. Cylinder Head or Engine Block Cracks
Cylinder and piston problems like excessive wear or scoring reduce engine power, cause engine knocking and increased fuel consumption. White smoke from the exhaust may be an indication that coolant is burning during the combustion process. These are serious issues that result from:
- Coolant contamination: Foreign particles may contaminate the coolant, compromising the integrity of various engine components. It can also cause cracks over time.
- Corrosion: Without proper maintenance, water or improper coolant weakens these parts’ metal, making them susceptible to cracking.
- Manufacturing defects: Metal issues that come up during production or manufacturing defects can also contribute to crack formation in the cylinder head or engine blocks.
- Overheating: Overexposure to heat due to cooling system failures, coolant leaks, or excessive leads causes thermal stress, eventually leading to cracks.
8. Coolant or Oil Leaks
Cooling system problems like coolant leaks, a malfunctioning thermostat, or radiator issues lead to engine overheating. What starts as a leak can cause serious engine problems if it is not addressed swiftly. Indicators of coolant leaks include coolant puddling under the truck, a sweet smell around the engine, low coolant levels, or an overheating engine.
The same problem occurs with oil leaks from gaskets, seals, or other components that reduce the engine’s oil levels. Incorrect gasket installation and high oil pressure both contribute to this problem. Drivers will notice visible oil spots or puddles under the truck with engine performance issues as components lack proper lubrication.
9. Engine Misfires
Engine misfires can result from worn or faulty camshafts and lifters. Damage to these parts leads to poor valve timing, which affects the engine’s performance and causes misfires, engine stalling, or power reduction. Other reasons engines can misfire are due to:
- Compression problems: Low compression in one or more cylinders is often the result of worn piston rings, a blown head gasket, or valve damage.
- Ignition system problems: Factors that disrupt the combustion process include faulty ignition coils, spark plugs, and spark plug wires.
Symptoms of this problem include a noticeable shaking or roughness when the truck engine is idling, slower acceleration, and excessive exhaust emissions. Technicians will inspect the spark plugs, fuel system, mass airflow sensor, or air intake system, or perform a compression test. They may also look to the EGR system, looking for clogs, malfunctions or leaks that can create engine misfires.
10. Fuel Efficiency vs. Engine Performance
Engine performance and fuel efficiency are closely intertwined aspects that result from common truck engine problems. Clogged air filters, malfunctioning mass airflow sensors, or air intake system problems can reduce engine efficiency, leading to increased fuel consumption and poor engine performance.
To strike a good balance between engine performance and fuel efficiency, you’ll need proper engine tuning, regular maintenance, and prompt responses to any engine concerns. Advanced diagnostic tools and technologies can help technicians rectify any problems early to prevent a significant knock on your fleet’s fuel efficiency. Using only high-quality fuel with the right fuel additives can boost combustion efficiency to increase fuel efficiency.
Recognizing Heavy-Duty Engine Problems
Slow acceleration and low engine power can result from any number of engine troubles. While this is easy to pick up, operators may need to look out for a few other key indicators. Training your fleet operators to recognize the signs of common truck problems allows them to communicate with technicians effectively. The long-term results are faster turnaround times for repairs and problem-solving.
Keep these aspects in mind to identify the most common engine problems:
- The check engine light: Drivers must report this immediately. The check engine light shows that the onboard diagnostic system identifies a problem.
- Starting challenges: Paying attention to delays or unusual sounds when starting the truck can result from problems in the battery, fuel delivery system, or starter.
- Unusual noises: Keep an ear out for clicking, hissing, or knocking sounds. These can show issues with engine components like the exhaust system, pistons, belts, or valves.
- Strange odors: Engine problems can also present through unusual smells like a sweet odor, burning oil or coolant.
- Power reduction: There may be a problem with the fuel system, the engine’s internal components, or the air intake when the truck’s overall performance decreases.
- Fluid leaks: Coolant, oil, or transmission fluid leaks often lead to decreased lubrication, which can overheat the engine or create transmission issues.
- Smoke emission: Excessive smoke can point to different engine issues. Blue or grey smoke may mean there is an oil leak due to damaged piston rings, work cylinder walls, or leaking valve seals. Black smoke means the truck is burning too much gas due to a blocked manifold, malfunctioning fuel injection system, or clogged air filter, among other issues. Nonstop milky white smoke can indicate a leaking head gasket, cracked block or cylinder head.
- Shaking or vibrations: Excessive vibration when the vehicle accelerates can suggest problems with the engine mounts or an imbalance in the engine.
- Irregular idling: Rough idling can indicate issues with the engine’s combustion process, spark plugs, or fuel system.
Heavy-Duty Diagnostic & Repair Tools From Noregon
Fleet managers and maintenance professionals play a vital role in heavy-duty truck engines’ ongoing reliability and performance. Today’s technicians need need the right diagnostic and repair tools to keep them running smoothly.
Noregon is the industry leader in commercial vehicle maintenance tools. More than 50,000 technicians trust JPRO diagnostic software and the award-winning technology of NextStep Repair with their commercial vehicle maintenance.