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Preventive Maintenance Checklist for Diesel Trucks

UTI Profile Image Universal Technical Institute Sep 24, 2019 ·

Whether you’re interested in becoming a diesel technician or drive a diesel truck yourself, it’s important to understand preventive maintenance and the purpose it serves.

Following a maintenance checklist is essential for maintaining your truck and keeping your equipment in good condition, which in turn protects the safety of both you and others on the road. Additionally, performing routine maintenance 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.

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 will also 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 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. 

Diesel Truck Maintenance Checklist

Diesel truck drivers should follow a 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.

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 FMCSR
  • 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 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 

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 level to the engine cooling system. 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

Air Brake Inspection

An air brake inspection is only performed on trucks equipped with air brakes. Brakes are a critical element to inspect, 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 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

Prepare for a Career as a Diesel Technician at UTI

At Universal Technical Institute, 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. To learn more, visit our Diesel Technology Program page and request information today.

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