Diesel Truck Maintenance: Essential Tips for Longevity

Whether you’re interested in diesel tech or drive a diesel truck yourself, it’s important to understand preventive maintenance and its purpose.

Following a diesel maintenance checklist is essential for maintaining your truck and keeping your equipment in good condition. In turn, you can help protect the safety of both yourself and others on the road.

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.

Plus, learn how you can get training for a career as a diesel technician and learn how to make these repairs yourself!

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. Regular maintenance will also help commercial truck operators avoid violation fines issued by the Department of Transportation. 

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

While some might consider routine maintenance a waste of time, it saves money in the long run. Investing the time and resources to maintain diesel equipment optimizes fuel economy and prolongs the durability of each part. Professional diesel technicians should understand the importance of preventive maintenance and the necessary inspections and repairs to keep their equipment running as efficiently as possible. 

Diesel Truck Maintenance Checklist

Before hitting the road, diesel truck drivers should follow a preventive maintenance checklist. 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.

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 meet Federal Motor Carrier Safety Regulations (FMCRs).
• Inspect floormat, gearshift and gearshift boot.
• Inspect foot pedals, pads and mounting.

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 & 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 & 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.

Tires/Wheels Inspection

Checking a diesel truck’s tires is critical during inspection. This involves examining every tire to ensure it’s properly inflated and meets the requirements for tread depth. 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: Everything You Need to Know About Heavy-Duty Truck Alignment

Diesel Engine Maintenance Checklist

Without a properly functioning engine, a diesel truck can’t run. So, to take a closer look at everything from the power steering level to the engine cooling system, diesel techs need to conduct engine inspections. A full diesel engine inspection 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 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: How Does a Diesel Engine Work?

Air Brake Inspection

Air brake inspections are only performed on trucks equipped with air brakes. Checking brakes 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 (ASA).
• 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 (ASA).
• Inspect trailer air hoses and couplers (tractors only).
• Replace air drier dessicant 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 the automatic traction control (ATC) warning light.
• Inspect stop light operation.
• Lubricate all brake component grease fittings (optional).

Hydraulic Brake Inspection

A hydraulic brake inspection is only performed on trucks equipped with hydraulic brakes. Hydraulic brakes use fluid to charge the brakes.

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 fitting 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 Hydraulic Anti-lock Braking System (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 back-up (reserve) system.
• Inspect HABS wiring harnesses, connectors for proper routing.

Diesel Truck Maintenance Schedule

An ideal maintenance schedule for a diesel truck may vary depending on how the vehicle is utilized. However, you should prioritize regular checks and servicing to ensure optimal performance and longevity. This schedule should include frequent oil and filter changes, typically every 5,000 to 7,500 miles, to maintain engine lubrication and prevent wear.

Regular inspection and replacement of air filters, fuel filters and coolant are essential to safeguard against contaminants and maintain proper engine function. Additionally, a comprehensive inspection of belts, hoses, brakes and the exhaust system should occur every 15,000 to 30,000 miles to identify signs of wear or malfunction.

Ensuring tire rotations, alignments and balancing every 6,000 to 8,000 miles can extend tire life and improve fuel efficiency. Regular maintenance of transmission, differential and steering fluids, usually every 30,000 to 50,000 miles, helps sustain smooth operation and prevents breakdowns.

Adhering to a diesel maintenance schedule like this helps mitigate unexpected breakdowns, enhances safety and maximizes the diesel truck's overall performance and longevity.

Diesel Truck Maintenance FAQs

How much does diesel truck maintenance cost?

The cost of maintaining a diesel truck can vary widely based on several factors, including the make and model of the truck, its age, usage, the region where maintenance is performed and the specific services needed. On average, routine maintenance for a diesel truck might cost anywhere from $1,000 to $2,000 per year, but this can significantly fluctuate.

Routine maintenance tasks like oil changes, filter replacements, fluid top-ups, tire rotations and inspections typically cost less compared to more significant repairs or part replacements such as engine overhauls, transmission repairs or brake system replacements. These major repairs can substantially increase the maintenance expenses.

Additionally, servicing from a dealership might be more expensive than getting maintenance done at independent repair shops or by performing some tasks yourself if you have the necessary skills and tools. If you’d like to learn these types of skills, you can train to become a diesel technician here at UTI!¹

READ: How to Become a Diesel Mechanic?

What is a good diesel truck maintenance schedule?

A good diesel maintenance schedule is essential for ensuring the longevity, reliability and optimal performance of your truck.

Always refer to the manufacturer's recommendations in the owner's manual as they might have specific guidelines tailored to your diesel truck model. Additionally, adapting the maintenance schedule based on driving conditions, load and environmental factors is recommended for diesel truck upkeep.

Do diesel engines require more maintenance?

In general, diesel or four-stroke engines don't necessarily require more maintenance compared to gasoline engines. However, they do have some distinct maintenance needs due to their design and combustion process

Prepare for a Career as a Diesel Technician at UTI

With hands-on diesel training from Universal Technical Institute, you can learn industry skills on equipment from leading brands in the field.¹⁸ This way, you can learn the fundamentals needed to service powerful trucks and engines.¹

In addition to the 45-week Diesel Technology program, we also offer a variety of manufacturer-specific advanced training programs.⁷ 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.¹¹

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