13 Common Heavy-Duty Truck Repair Issues

If your vehicle weighs 33,000 lbs (15,000 kg) or more, it is considered a heavy-duty truck falling under classes 7 and 8 in the truck classification.

Because heavy-duty trucks carry heavy loads over long distances, they often develop mechanical issues that your mechanic must fix before going on another trip.

With a truck maintenance checklist, you can easily identify common breakdown issues affecting the efficiency of your semi-trailer and schedule preventive maintenance to fix them early before the damages become extensive, leading to expensive repairs.

In this article, we have outlined common mechanical issues associated with your heavy-duty truck, their causes, and the solutions for fixing them. 

Keep reading for more information.

13 Common Heavy-Duty Truck Repair Issues, Their Causes, and How to Fix Them

1. Brake Failure

An effective braking system is essential for your heavy-duty truck. This system will help your vehicle make necessary stops when you reach your destination, encounter traffic jams, or stop at traffic lights without causing accidents.

The Federal Motor Carrier Safety Administration (FMCSA) has issued a regulation that requires you as a fleet manager, truck driver, or truck owner to inspect your vehicle to assess the effectiveness of its braking system and service and repair it to ensure they meet the standard requirement and function well.

According to a report from FMCSA to Congress, 29.4% of truck accidents relate to brake failure. The statistics also show that about 27% of fatal accidents involve single truck units, while 76% are associated with tractor-trailers.

Signs of a Malfunctioning Brake in Commercial Trucks

Here is a list of signs to alert you of a faulty braking system in your heavy-duty truck.

• An increased speed when going downhill
• Strange squeaking and grinding noises when applying brakes
• Your truck is dragging forward even after braking
• Soft feel on the pedal brakes
• Your vehicle is pulling to one side when you apply the brakes
• A red warning brake sign on the dashboard
• Strong pulsations on the pedal brakes

Causes of Brake Failure in Heavy-Duty Trucks

These factors are making your truck’s braking system fail to function well. 

• Worn-out brake drums and brake lining
• Twisted or uneven wear of the rotor disks
• Damaged or missing mechanical elements, including springs, anchor pins, pushrods, spiders, cam rollers, mounting bolts, shoes, lining, and pads
• Loose camshafts, spiders, and air chambers
• Hydraulic leaks
• Over-adjustment of the pushrod stroke
• Overheating the brake pads makes them stiff and unable to grip the rotor disk.
• Decrease of pressure in the hydraulic brake fluid
• Overloading your truck

How to Fix the Brake Issues in Your Truck

You need to diagnose your braking system to understand why they are not functioning as required.

If your brakes fail because of a minor issue, like mud or water on the brake pads lubricating them, you can clean them to make them more efficient.

You can contact the nearest heavy-duty truck repair shop near you and get help from an experienced mechanic.

2. Faulty Ignition System

You want to set out to pick up goods or deliver them to your client’s destination. You start your truck expecting your engine to ignite, but instead, it produces a cranking sound. I know how disappointing this can be. 

Sometimes, when you try to start your truck, it may not start because the electrical power from the battery isn't reaching the starter motor. This can happen because there is insufficient power supply from the battery to the starter motor.

Moreover, the starter motor could fail to convert electrical energy into mechanical energy needed to start the engine. In either case, the engine won't start.

What Makes Your Diesel Truck Fail to Start?

Here is a list of the possible reasons why your truck fails to start and produces a dim interior light and a clicking sound.

• Drained or dead battery
• Clogged fuel filter, faulty fuel tank, or insufficient fuel or gas
• Faulty fuses or wiring systems
• Defective solenoid and starter motor
• Worn-out spark plugs
• Malfunctioning ignition coils, ignition switches, engine sensors, or the computer system

How to Solve Ignition Issues in Your Commercial Truck

Check your battery to identify any loose cables to fix them or corrosion on battery terminals and clean them. 

To jump-start your battery, connect your truck to a functioning vehicle using a set of jumper cables. Allow the battery to charge for about 10-15 minutes before starting your car.

If your battery, spark plugs, or starter motor are dead, consider replacing them to solve the issue.

Seek help from a professional diesel truck mechanic near you.

3. Clutch Issues

The clutch system connects your truck's driveline, engine, and transmission. This connection allows you to shift gears and control your truck's speed.

If the clutch system in your large truck is faulty, it won't work correctly. This can disrupt your fleet's operations and increase downtime costs. After each trip, check your clutch for issues to avoid costly repairs on other parts.

Indicators of a Clutch Problem in Your Truck

• Spongy/loose clutch pedal
• Increase in the engine’s acceleration without an increase in speed
• Screeching noises that originate from the clutch when you accelerate or decelerate
• A worn-out clutch may be sticky and fail to engage
• Increased vibrations on the steering wheel when you increase the speed
• The presence of an unpleasant odor when the clutch bearing heats
• Gears are stiff or produce a grinding sound when shifting

Causes of Clutch Failures in Your Big Rig

• Faulty clutch linkage or hydraulic system
• Worn-out clutch cables, discs, lining, spline, springs, guide tube, flywheel bearing, release arm pivot, engine mounts, and CV joints
• Transmission and engine leaks
• Misaligned clutch disc
• Locked travel pedal 
• Greasy surfaces

How to Fix the Clutch Issues in Your Heavy-Duty Truck

Once you realize an issue with your clutch system, do not hesitate to contact a nearby truck repair shop or a mobile truck repair mechanic to help you diagnose and fix the problem.

4. Malfunctioning Exhaust System

An exhaust system is another crucial part of your heavy-duty truck. It helps emit poisonous gases and smoke from the engine cylinder to ensure the driver and passengers are safe.

The muffler in the exhaust system is also essential, as it helps suppress noise from your truck and ensures a smooth ride.

A faulty exhaust system can cause your truck to fail to perform its functions as required, which can lead to severe problems.

How to Tell if Your Heavy-Duty Truck Exhaust System Has Issues

• A defective exhaust system will make your vehicle consume a lot of fuel
• Noticeable rust or other visible damage around the exhaust pipes
• Loud engine roar and exhaust noise than usual
• The presence of exhaust smoke and odor inside your truck’s cabin
• The check engine light turns on, resulting from an issue with the faulty exhaust components

Causes of Exhaust Failure in Semi-Trucks

• Defective oxygen sensors
• Leaks in the exhaust system and combustion chambers
• Faulty catalytic converter
• Broken hangers, mufflers, brackets, and insulators
• Blocked exhaust system

How to Fix a Defective Exhaust System in Your Truck

A certified truck mechanic will diagnose your exhaust system, identify problems affecting its performance, and recommend actions.

Note that some faulty components of your truck's exhaust system will need to be replaced, while others require repair and cleaning to ensure they function effectively.

5. Faulty Engine

The engine is the central part of your commercial truck. It must work efficiently for your vehicle to operate and perform its functions appropriately. 

As a fleet manager, truck driver, or truck owner, you need to inspect your engine regularly to identify any upcoming issues and have them fixed. This will keep your truck running and avoid further damage and downtime costs.

Indicators of a failing engine system

• The check engine light on your truck dashboard turns on
• Strange smells and noises from the engine
• Unusual black smoke emanating from the exhaust
• Unexpected power loss
• Decreased efficiency in fuel consumption
• When the ignition key is on or off, your truck fails to start or shut down
• Overheating of your truck’s diesel engine
• The presence of oil stains below the truck

Causes of engine failure in heavy trucks

• Dead or drained battery
• Faulty turbocharger
• Insufficient fuel, gas, and coolants
• Clogged air filters and fuel injectors
• Defective fuel sensors and electric plugs
• Overloading
• Contaminated diesel

How to fix engine problems in your commercial truck

A professional mechanic will troubleshoot your engine to identify issues and fix them. 

As a truck owner or fleet manager, you can train your driver to fix minor issues like cleaning a clogged fuel filter.

6. Defective Axle

Axles are essential for your truck as they help it bear its weight, propel heavy loads on the road, and remain stable. 

Different types of axles in your big rig work together to enable your truck to perform its intended duties and ensure the safety of your driver and other road users.

The axles support a lot of weight and are prone to severe stress and strain that may damage them.

Below is a list of the causes of the signs of malfunctioning axles and their axles.

How to Tell if Your Truck’s Axles are Faulty

• Unstable feeling or swaying of the tractor-trailer when you make turns or during wet days 
• Uneven tire wear
• The presence of fluid around the tire results from leaking axle seals
• Excessive vibrations on the steering wheel or the entire vehicle
• Strange clunking or clicking noises
• Misaligned steering wheel
• Unusual overheating of the trailer wheels
• Your trailer’s brakes are not performing appropriately

What Leads to Axle Failure in Your Heavy-Duty Truck?

• Misaligned axles and tires
• Rough roads
• Overloading
• Accidents
• Defective seals 
• Low level of axle lubricants

A professional truck mechanic will diagnose your truck and trailer to identify and fix the axle problem. 

When you doubt the axle problem or identify the above signs, contact your truck mechanic or a nearby mobile mechanic or truck shop for help.

7. Suspension System Failure

The suspensions in your heavy truck will help contain road shocks and keep your vehicle stable, ensuring your truck driver and passengers are safe and enjoy the ride.

Indicators of a Failing Suspension System in Your Heavy-Duty Truck

• Your truck pulls constantly to the opposite side
• Uneven wear on the tire
• Strange clunking or cracking noises
• Excessive vibrations and bounces on pumps and rough roads
• One side of your truck is lower than the other, or you notice your vehicle having a lower height than usual
• A loose steering wheel can sometimes result from a suspension issue
• Sometimes, you may notice your vehicle tilting or leaning to one side, which indicates that one of the suspensions is damaged

Causes of Suspension Failure in Your Commercial Truck

• Worn-out ball joints, struts, shock absorbers, control arms, bushings, and u-bolts
• Low levels of suspension fluids
• Leaking shock absorbers

Since this is a significant problem, an expert must inspect and repair it. If you identify any of the signs above, contact a nearby truck repair shop to have your suspensions fixed.

8. Faulty Electrical System 

The alternator, starter motor, and battery work harmoniously to produce electric power that will run your truck.

An electric failure may affect the overall performance of your truck's parts, such as the wipers, radio, lights, locks, and air conditioning system.

How to tell if your Big Rig Has an Electric Issue

• You notice your lights are flickering or dim.
• Your truck battery loses power and dies unexpectedly
• You turn the ignition key, and your truck fails to start or produces a grinding noise
• A burning smell that could be from overheating circuits and wires
• Some glitches or potential shutdown of your truck’s electric accessories like radio or GPS
• You realize the voltage fluctuations on the dashboard voltmeter

Causes of Electric Failure in Heavy-Duty Trucks

• Blown fuse and damaged or disconnected wires
• A dead or drained battery leads to a lack of power supply
• Faulty alternators and starter motor

With a multimeter, your truck's licensed electrician can identify all the electrical challenges interfering with your vehicle’s performance, provide suggestions on how to fix them, and even solve the problem.

9. Wheel and Tire Problems

The tire system in your truck rotates to cover distances while hauling heavy loads from place to place. 

Regular and early preventive wheel and tire maintenance will save you money on roadside and downtime costs and increase the lifespan of your truck.

Consider inspecting your truck before and after trips to have any issue addressed by a certified mechanic. 

What are The Signs of a Failing Tire System?

• Strange squealing sound from the tires
• You realize your truck is consuming more fuel than usual
• Uneven tire wear on the side and center
• Your steering wheel is off the center even when driving on a straight road, and the tire wheels are aligned.
• You are driving on a straight road, and your truck pulls to one side
• Cracks on the tire sidewalls
• Your truck tire bursts

Causes of Tire Problems in Your Heavy-Duty Truck

• Misaligned tires
• Under-inflation can cause your tire to bulge out and burst because of the heavy weight of your truck and the heat and friction of driving.
• Sharp objects pierce your tire, making it release pressure.

How to Fix Tire Issues in Your Vehicle

• Always inspect your tires to identify any piercing objects stuck on the tire and remove them.
• Inflated your tires to their standard levels
• Seek help in case your tire has leaks or cracks
• Contact an expert to check your tire alignment. Proper alignment ensures a smooth ride.

10. Air Conditioning(AC) System Failure

A functioning air conditioning system(AC) will help you adjust your truck's interior temperatures to ensure you enjoy your road trip during hot and cold seasons.

As a truck driver, truck owner, or fleet manager, you should always inspect the ACs of your trucks regularly to ensure they are operating well for the well-being of your passengers and vehicle.

Signs of a Defective AC System in Your Commercial Truck

• When you turn on the AC, there is a strange clanging or squealing noise
• Your AC blows warm air instead of cold air
• Your AC keeps running even after shutting down
• A failing compressor will fail to start or stop even unexpectedly
• You notice varying temperatures from different vents
• A foul smell originating from your AC
• Your electric AC fans fail to operate when the truck is not moving
• You notice a black dead substance around the AC compressor. The substance is typically mold
• The presence of fluid leaks around the AC compressors

Causes of AC Malfunction in Your Truck

• Low refrigerant levels
• Punctures in the compressors, hoses, evaporators, condensers, and O rings
• Faulty expansion valves, thermostats, and evaporator coils
• Clogged air filters
• Blow fuses, damaged circuit breakers, and disconnected wires
• Overheating engine
• Loose belts
• Using the wrong refrigerant or mixing non-compatible refrigerant oils leads to the production of the black substance.

How to Fix AC Issues in Your Heavy-Duty

• Ensure there is enough refrigerant in your AC.
• Always clean your AC’s air filters to ensure they blow clean air and function correctly.
• You can also use a suitable refrigerant for your commercial truck to function appropriately.
• If you notice any of the above signs, visit the nearest truck repair shop to have your AC fixed by a certified mechanic.

11. Faulty Fuel System

The fuel system in your truck stores diesel and supplies it whenever your vehicle needs it for smooth operation.

Therefore, inspecting, repairing, and maintaining your truck’s fuel cells is necessary to increase its lifespan and fuel efficiency.

Here are Some Signs of a Faulty Fuel System That You Should Keep in Check

• You notice your truck consumes much more fuel than usual on the same distance.
• Inconsistent acceleration
• Sudden power loss while in transit
• You experience a clunking or sputtering noise from the engine system
• You put on the ignition key, and your truck fails to start
• You notice a cloud of black smoke coming from your truck’s exhaust

Causes of failed fuel system in heavy-duty trucks

• Clogged fuel filters
• Leaking or clogged injectors
• Worn-out fuel lines and fuel pumps
• Contaminated fuel

How Do You Fix Fuel System Issues in Your Heavy Truck?

After identifying the triggers of a malfunctioning fuel system, you can choose to fix minor issues like clogged fuel filters and injectors if you know how to do so.

Other issues are complicated and require a certified truck mechanic to fix. Contact a mechanic or visit a nearby truck repair shop for help.

12. Transmission Issues

Your truck’s transmission system consists of complex gears that work together with the clutch to enable your 18-wheeler to haul heavy loads from place to place.

Understanding the different transmission systems available will enable you to choose the correct transmission for your truck, allowing it to manage heavy loads and sustain extreme torques.

A transmission problem in your heavy-duty truck can halt the productivity of your fleet or truck and result in losses. Since the transmission systems are crucial for your vehicle's optimal performance, they need regular checks and maintenance.

How can you tell if your transmission system needs repair or replacement?

Here are Some Signs of a Faulty Transmission System in Your Truck.

• Clunking, whining, or grinding noises when shifting gears
• The presence of leaks under your truck
• Sticky, slipping, or slipping gears.
• The check engine light turns on.
• A burning smell from your truck’s transmission or engine system
• Excessive vibrations 
• High temperatures originating from the transmission system

Causes of Transmission Failure in Heavy Trucks

• Low levels of transmission fluids
• Worn-out gaskets, synchronizer rings, torque converter, gears, seals, and clutch
• Faulty solenoids
• Jammed gears

Visit a nearby truck mechanic repair shop to inspect your transmission and fix any issues. 

You can also contact a mobile truck repair mechanic to have your vehicle serviced on the roadside.

13. Faulty Steering and Horn Systems

Remember that a well-maintained steering system is essential for your heavy-duty truck to maneuver corners, stay in its lane, and overtake other vehicles while carrying heavy loads.

To ensure the safety of your truck driver and others on the road and reduce the risk of accidents that could disrupt your fleet's operations, regularly inspect the steering system to ensure all its parts are in good condition.

The horn system is part of the steering system. It allows your truck driver to communicate with other drivers and road users by signaling and alerting them to their presence, helping to prevent accidents caused by poor driving.

As a fleet manager, truck owner, or truck driver, always check your vehicle to ensure the steering and horn system meets the Federal Government's regulations and other safety rules.

How do you tell if your steering and Horn Systems are faulty?

• Your steering wheel drifts even when the tires are straight and you are driving in a straight lane.
• The presence of steering fluid leaks around the steering wheel
• Increased vibrations when turning the steering wheel
• Your steering wheel is loose and, therefore, slacks off
• Your steering wheel becomes stiff, and you may need extra energy to turn it
• A clunking or grinding noise from the steering system when making turns
• Take note of a clicking noise when you apply the horn
• Sometimes, the horn may be hard to engage or fail to produce a sound
• Visible damage on the horn relays

Causes of Malfunction Steering and Horn Systems

• Worn-out ball joints, hoses, seals, steering gears, tie rod ends, and bushing
• Misaligned tires
• Leaks on the steering fluid reservoirs
• Twisted rims
• Low steering fluids
• Lose connection or blown fuses and wires in the horn relays
• Worn out relays

To address the steering and horn issues, you require an experienced mechanic to diagnose them using a multimeter to identify the problems and offer solutions.

Conclusion

Note that no issue is too big or too small on your truck. Once you encounter any of these issues, do not hesitate to get help from an experienced mechanic. Our experienced TruckUp mobile mechanics are available 24/7 to help with all your truck's mechanical issues, whether at home, on the roadside, in public parking, or anywhere else. Just choose your location and share your details. A professional and experienced mobile mechanic in your region will contact you and arrange to repair your truck.

Frequently Asked Questions(FAQs)

1. Why Do Heavy-Duty Trucks Need Regular Maintenance?

Heavy-duty trucks require regular and timely maintenance to address potential issues, prevent breakdowns and downtime, and ensure safe and reliable operation. Always schedule a preventive maintenance schedule that will help you inspect your truck to have any problem fixed.

2. What Type of Trucks are Heavy-Duty Trucks?

Heavy-duty trucks fall under classes 7 and 8 of trucks since their Gross Vehicle Weight Rating(GVWR) ranges between 26,001 to 33,000 pounds. They include semi-trucks, dump trucks, tractor-trailers, city transit buses, mobile cranes, cement mixers, 18-wheelers, and sleeper cabs.

3. Which Industries Do Heavy-Duty Trucks Serve?

Heavy-duty trucks are essential for serving customers in various industries, such as construction, mining and quarrying, agriculture, oil and gas, freight and logistics, public utilities, and waste management.