Diesel Truck Maintenance Guide

Preventive maintenance is key to keeping diesel trucks running.

Whether you’re interested in becoming a diesel technician or drive a diesel truck yourself, following a truck preventive maintenance checklist is essential for maintaining trucks and keeping equipment in good condition, which in turn protects the safety of both you and others on the road. Routine diesel truck maintenance also prevents the need for frequent replacements and keeps repair costs to a minimum.    

If you’re looking to learn more about diesel truck maintenance, you’ve come to the right place. Follow along as we share what preventive maintenance is, its importance and a complete diesel truck inspection checklist!    

Key Summary Points

• Preventive maintenance is crucial for diesel trucks, extending their lifespan, improving fuel economy and maintaining their resale value. Regular maintenance also helps avoid costly breakdowns and Department of Transportation fines.
• Diesel truck maintenance involves routine inspections based on mileage or time to keep the equipment in optimal condition, saving money in the long run by optimizing fuel economy and prolonging the usage of each part.
• A comprehensive diesel truck inspection checklist includes in-cab inspections (seat condition, warning lights, horn operation, etc.), pneumatic system checks (air system leaks, air dryer operation, etc.), cab and body inspections (bumpers, cab door locks, fuel tanks, etc.), and tire and wheel inspections (tread depth, tire pressure, lug nuts, etc.).
• Diesel engine maintenance is critical for the truck's operation, requiring checks on the radiator, A/C components, power steering, fuel/water separator, engine leaks and air intake system. It also includes changing engine oil and filters, and servicing the air filter as needed.
• Air brake and hydraulic brake inspections are vital for trucks equipped with these systems, checking everything from brake chambers and lines to the operation of brake pedals and hydraulic brake booster systems.

Read: Diesel Terminology Explained

Diesel Truck Maintenance: Understanding the Basics

Preventive maintenance, when performed regularly, can extend the lifespan of diesel trucks and improve fuel economy. It can also play an important role in sustaining a truck’s value in resale, as buyers usually want to see the vehicle’s full maintenance record before making their purchase. For a commercial trucking application, performing regular maintenance can also help avoid fines for Department of Transportation violations.

If you’re familiar with diesel trucks, you know that sudden mechanical breakdowns are expensive—however, they can often be avoided with routine inspections. These maintenance checks can be performed based on mileage or time.

While some might consider routine maintenance to be a waste of time, it saves money in the long run. Investing the time and money to keep diesel equipment in good condition optimizes fuel economy and prolongs the usage of each part. Skilled diesel mechanics understand the importance of preventive maintenance and are able to complete the necessary inspections and repairs to keep their equipment running at the highest efficiency.

Read: Diesel Careers

Maintenance on diesel trucks: what you need to know

Keeping your diesel truck in tip-top shape ensures reliability, longevity and minimal financial wastage. Let’s break down the core aspects of diesel truck maintenance.

Regular oil changes

Changing your oil regularly ensures that everything runs as smoothly as possible—and with improved fuel efficiency. Make a habit of checking your oil levels and using the right type of oil recommended for your truck.

Fuel filter replacements

A clean fuel filter is essential for optimal engine performance. Diesel engines tend to attract dirt and debris, so keep an eye on your fuel filter and change it out as needed. This simple step will help prevent clogging and other fuel-related issues down the line.

Air filter checks

Regularly checking and replacing the air filter ensures your engine gets the clean air it needs for combustion. Cleaner air means better efficiency and longevity for your diesel vehicle.

Read: Becoming a Diesel Fleet Mechanic

Coolant system maintenance

Your truck’s coolant system plays a crucial role in preventing overheating. Schedule regular inspections of your coolant levels and hoses, and ensure your system is flushed and refilled as needed to keep things cool under the hood.

Brake inspections

Regular brake inspections are vital for safety. Check the brake fluid levels and inspect the pads for wear and tear.

Tire care

Regularly check tire pressure, tread depth, and alignments to ensure safe and efficient handling. Plus, properly maintained tires can save you money on fuel.

By keeping these key maintenance points in mind, your diesel truck will not only be ready to hit the road but will also give you the peace of mind that comes with knowing you’ve done everything to keep it in great shape.

Read: Diesel Service Manager Explains the Benefits of a Career in Diesel

Diesel Truck Maintenance Checklist

Diesel truck drivers should follow a truck preventive maintenance checklist prior to hitting the road for each trip. This involves checking the important elements of the truck, including lights, tires, turn signals, hazard lights and much more. Those completing the inspection should watch out for unusual sounds and basic warning signs that indicate the need for repair, such as fuel contamination, oil oxidation or a black exhaust problem.

Follow along as we share a complete diesel truck inspection checklist, broken down by in-cab inspection, pneumatic system check, cab and body inspection, tire and wheel inspection, engine inspection, air brake inspection and hydraulic brake inspection.

Diesel truck maintenance schedule

Establishing a proper diesel truck maintenance schedule will help maintain your vehicle’s longevity and performance. Here’s a handy guide to keep your truck running smoothly:

• Daily checks: Conduct quick checks before you hit the road, including tire pressure, fluid levels and ensuring that all lights are functioning.
• Weekly checks: Take a deeper dive into those fluid levels—oil, coolant and brake fluid—and give the air and fuel filters a good visual inspection. If anything looks off, address it right away.
• Monthly maintenance: Inspect the belts and hoses for wear, flush the coolant system if needed, and give your brakes a thorough once-over to prevent any surprise issues.
• Every 6 months or 10,000 miles: This is the time to get serious! Change the oil and oil filter, replace the air filter, and have the transmission and differential fluids checked. A little extra attention now will keep your truck happy on long hauls.
• Annually: Schedule a full inspection that includes everything from the engine to the tires, ensuring you catch any issues before they become major repairs. It’s also a great time to check exhaust systems, suspension components and more.

Read: 3 Ways UTI’s Diesel Mechanic Trade School Can Prepare You for a Career

In-Cab Inspection    

The in-cab portion of a preventive maintenance check covers everything from the windshield to the foot pedals.

• Check seat condition, seat suspension and seat belt operation.
• Check ignition key and start button.
• Check warning lights and alarms.
• Check interior lights (including dash and gauge illumination).
• Check dash gauges.
• Check air gauges (and low-pressure warning devices).
• Check horn operation.
• Check A/C, heater and defroster controls.
• Check dash switches and accessory operation (PTO, cruise, etc.).
• Check clutch pedal operation.
• Check automatic transmission selector/wiring.
• Check driveline parking brake operation.
• Check steering operation.
• Inspect sun visors.
• Check windshield and door glass for obstruction or damage.
• Check wiper/washer operation.
• Verify safety equipment decals, reflectors, flares and fire extinguisher meets FMCSRs.
• Inspect floormat, gearshift and gearshift boot.
• Inspect foot pedals, pads and mounting.

Read: Train for a Career That’s In-Demand: Advice From a Diesel Employer

Pneumatic System Check

The pneumatic system uses compressed air to transmit and control energy. Checking this system involves everything from analyzing the air system for leaks to inspecting treadle valve operation.

• Check air system for leaks (brakes released and applied).
• Record governor specs.
• Check tractor protection valve.
• Test air pressure build-up time.
• Check air dryer operation (purge and cycle heater).
• Inspect treadle valve operation (lube pivot and roller).
• Inspect air compressor (leaks and air filter condition).

Cab and Body Inspection

The cab and body inspection covers a wide range of parts, from the air compressor to the bumpers.

• Check air system for leaks (brakes released and applied).
• Record governor specs.
• Check tractor protection valve.
• Test air pressure build-up time.
• Check air dryer operation (purge cycle and heater).
• Inspect treadle valve operation (lube pivot and roller).
• Inspect air compressor (leaks and air filter condition).
• Inspect bumpers and license plate bracket.
• Inspect cab body floor and door seals.
• Inspect cab door locks, latches and hinges.
• Inspect roof and wind deflector mounting.
• Inspect towing/hitch device (pintle hook).
• Inspect mudflaps/splash guards and brackets.
• Inspect/lube lift gate (if equipped).
• Inspect fuel tank(s), mountings, crossover lines and fuel caps.
• Inspect exhaust system and mounting.
• Check HVAC air inlet filters and ducts (service as needed).
• Inspect cab mountings, valve linkages and ride height (if equipped).
• Lubricate all cab, body and hood grease fittings.

Read: From UTI Grads to Diesel Employers: What These Alumni Look For in Hiring

Tires/Wheels Inspection     

Checking a diesel truck’s tires is a critical step in the inspection process. This involves examining every tire to ensure it meets the requirements for tread depth and is properly inflated. This can help to avoid problems with alignment, traction, framework, braking and steering.

Front

• Check wheel bearing and lube cap.
• Inspect for irregular wear patterns.
• Inspect for cuts and sidewall damage.
• Check and record valve stem caps.
• Inspect and record tread depth.
• Check and record tire pressure (psi).
• Inspect for loose lug nuts.
• Inspect for cracked or damaged wheels.

Rear

• Check wheel bearings and axle flange seal for leaks.
• Inspect for irregular wear patterns.
• Inspect for cuts and sidewall damage.
• Check for dual mating with square.
• Check and record tread design.
• Check and record number of valve stem caps.
• Inspect and record each tread depth.
• Check and record each tire pressure.
• Inspect for loose lug nuts.
• Inspect for cracked or damaged wheels.    

Read: Diesel Service Manager Explains the Benefits of a Career in Diesel

Diesel Engine Maintenance Checklist

Without a properly functioning engine, a diesel truck can’t run. An engine inspection requires a closer look at everything from the power steering fluid level to the engine cooling system. A full diesel engine maintenance checklist includes the following:

• Check radiator mountings for looseness or cracks.
• Check A/C condenser mountings for looseness or cracks.
• Check A/C compressor mounting and lines.
• Check for excessive play in water pump shaft.
• Check vibration damper for cracks, bulges, shifting or damage.
• Inspect coolant hoses and pressure test cooling system.
• Inspect coolant recovery system and pressure test radiator cap.
• Test and record antifreeze protection.
• Check alternator mounting and wiring.
• Check all accessory drive belts for condition and tension.
• Check power steering fluid level/filter and hoses.
• Drain fuel/water separator (if equipped).
• Check engine for leaks (oil, fuel and coolant).
• Check air intake system, CAC, piping, hoses and clamps.
• Inspect turbocharger for leaks (visual inspection only).
• Check engine wire harnesses, connectors and seals for damage.
• Obtain engine oil sample.
• Change engine oil and oil filters.
• Flush engine cooling system.
• Check operation of the engine fan clutch assembly.
• Service air filter only as needed, reset restriction indicator.

Read: What Skills Can I Learn at Diesel Mechanic School?

Air Brake Inspection

An air brake inspection is only performed on trucks equipped with air brakes. This inspection is critical, especially before a long trip. A compressed air brake system is a type of friction brake in which compressed air presses on a diaphragm and applies pressure to the brake pad that stops the vehicle.

The diaphragm in the brake chamber converts air pressure into mechanical force. These types of brakes are typically found in large, heavy vehicles, like diesel trucks.

• Inspect front brake chambers and air lines.
• Inspect and record front brake lining/pad condition and thickness.
• Inspect and record front brake drum/rotor condition.
• Check operation of both front automatic slack adjusters (ASAs).
• Inspect rear brake chambers and air lines.
• Inspect and record rear brake lining/pad condition and thickness.
• Inspect and record rear brake drum/rotor condition.
• Check operation of all rear automatic slack adjusters (ASAs).
• Inspect trailer air hoses and couplers (tractors only).
• Replace air drier desiccant cartridge (C-level inspection only).
• Check operation of the hand brake valve (trolley valve).
• Drain air tanks and check for contamination.
• Perform anti-lock brake system (ABS) operational self-test.
• Check ABS brake system wire harnesses and connectors.
• Check automatic traction control (ATC) warning light.
• Inspect stop light operation.
• Lubricate all brake component grease fittings (optional).

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Hydraulic Brake Inspection

A hydraulic brake inspection is only performed on trucks equipped with hydraulic brakes, which use fluid to get charged. When the brake pedal is pressed, the increase in hydraulic fluid pressure forces the brake pistons to push the brake pad against the rotor or drum. This causes friction and slows the wheels to stop the vehicle.

• Inspect front brakes and lines.
• Inspect master cylinder and fluid condition.
• Inspect power brake booster/hydrovac.
• Inspect all hydraulic lines, valves, hoses and fittings for leaks.
• Inspect and record front brake lining/pad thickness and condition.
• Inspect and record front brake/rotor drum condition and thickness.
• Inspect rear brakes and lines.
• Check driveline parking brake operation.
• Inspect pressure differential valve and warning light.
• Check HABS warning lamp indicator operation.
• Check hydraulic brake malfunction indicator lamp.
• Check proper brake pedal free travel.
• Check operation of the brake pedal: travel, effort and feel.
• Check operation of hydraulic brake booster system.
• Check operation of brake booster system.
• Check operation of brake booster backup (reserve) system.
• Inspect HABS wiring harnesses, connectors for proper routing.

Diesel Truck Maintenance FAQs

1. What are the key items included in a diesel engine maintenance checklist?

The key items in a diesel engine maintenance checklist include:

• Checking the radiator mountings.
• Inspecting coolant hoses.
• Verifying the operation of the air intake system.

Additionally, monitoring oil levels, replacing filters and testing the cooling system's pressure are essential steps to ensure optimal engine performance. Regularly following this checklist helps in identifying potential issues before they escalate into pricier, more dangerous complications.

2. How often should a diesel truck undergo preventive maintenance?

Preventive maintenance for a diesel truck should typically be performed monthly, every 6 months or 10,000 miles, and annually. This structured schedule ensures that all critical systems, from the engine to the tires, are thoroughly inspected and serviced, minimizing the risk of breakdowns during operation. Keeping this rhythm maintains the truck's longevity and reliability on the road.

3. What signs indicate that a diesel truck needs immediate maintenance?

Immediate maintenance may be required if you notice warning lights illuminated on the dashboard, unusual noises from the engine or a decrease in braking performance. Additionally, if you observe fluid leaks or changes in the truck's handling, it’s crucial to act quickly to avoid more significant problems. Recognizing these signs early can save time and reduce repair costs down the road.

4. How does the maintenance schedule for a diesel truck differ from that of a gasoline truck?

The maintenance schedule for diesel trucks is often more rigorous due to their different operating systems and heavier workloads. For example, diesel engines typically require more frequent oil changes and inspections of air intake systems, as well as checks of the turbocharger and fuel injectors. Understanding these differences ensures that diesel trucks operate efficiently and safely.

5. Are there any specific environmental considerations to keep in mind when maintaining a diesel truck?

When maintaining a diesel truck, it's essential to consider the environmental impact of emissions and fuel consumption. Regular checks of the exhaust system and adherence to emission standards help mitigate environmental harm. Additionally, using eco-friendly lubricants and correctly disposing of hazardous materials can further decrease your truck's environmental footprint.

Read: 5 Reasons You Should Consider Going to Diesel Mechanic School

Learn Diesel Truck Maintenance Skills at UTI!

At Universal Technical Institute (UTI), you can gain the fundamentals you need to service powerful trucks and engines while receiving hands-on training with equipment from leading brands in the industry.^1,18

In addition to the 45-week Diesel Technology program,⁷ we also offer a variety of Manufacturer-Specific Advanced Training programs(MSATs). This training can take your knowledge to the next level and help prepare you for a career working in a particular industry or for a certain manufacturer.

To learn more about training at UTI, request information online or by calling us at 1-800-834-7308 today. We’ll get you in touch with an Admissions Representative who can help guide you on your journey to becoming a technician!

UTI Campuses That Offer Diesel Mechanic Training

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