How to Inspect a Used Heavy-Duty Truck.
Buying a used heavy duty truck is complicated. Even if you’re mechanically inclined and try to do your own inspection, you might miss a defect that could be costly to repair. Read on to learn how to inspect a used heavy-duty truck as we focus on a five specific systems in detail: powertrain, suspension/steering, brakes, lighting system, and tires/wheels. We’ll outline the components to check and problems to look for during a used semi-truck inspection.
Simply put, the powertrain system produces and converts energy to move a vehicle. This system includes the engine, transmission, and driveshaft. Some basics to check:
Engine Compartment
The engine should look clean, without caked-on grease and oil. Check the level of the engine oil, which should be filled according to factory specs. The condition of the engine oil is something to take very seriously. A safe bet is to get an engine oil analysis to test your oil’s viscosity and to check for the presence of fuel, water, coolant and dirt in the oil.
Once the engine is warmed up, check the exhaust for blue or white smoke, either of which could indicate that the engine burns oil.
Check the coolant reservoir. Is it securely attached? Check for cracks, leaks and bends in the reservoir. Hoses attached to the coolant reservoir should be free of wear and tear.
Check the level of coolant fluid, which should be topped off and greenish in color. Use the correct type and amount of coolant according to factory specs.
Check the air filter. Do you see excessive dirt?
Check the transmission fluid color, smell and level. A burnt smell is never good and could forewarn you of transmission problems.
Start the engine. Do you hear any knocking noises? Thuds? After the engine has been running, check your oil, coolant, air, and fuel lines to make sure there are no leaks underneath the truck.
Check the belt driven alternator. Is it securely attached? Make sure all wires are connected. The belt itself should be free of cracks and frays.
Check the general hoses, driver and passenger side. Make sure hoses are securely attached. You should see no abrasions, cuts, bulges, or leaks.
Check the belt-driven water pump for secure attachment. Check for leaks, cracks, bends, or breaks. The belt should be free of cracks/frays.
Drive Train
Check universal joints, yokes, drive shafts, boots/seals, center bearings, and mounting hardware for wear and tear and looseness of parts. Check for proper phasing.
Check axle housing(s) for cracks and leaks.
Inspect axle breather(s)
Check drive train grease fittings: Make sure they are lubricated.
Check drive axle(s) oil for proper level, type and condition.
Check transmission wiring, connectors, seals, and harnesses for damage and proper routing.
Check interaxle differential lock operation.
Check transmission range shift operation.
Learn more about drive trains.
When all’s well with your suspension, you’ll be able to steer easily, even on rough terrain. Your suspension should also maintain correct axle alignment and spacing. You should have a smooth ride whether your truck is loaded or unloaded. Some basics to check:
Identify rough ride problems:
When cornering, does the truck force you to slow down more than usual?
Does the truck dip forward when you apply the brakes?
Is steering difficult when riding over bumps in the road?
Check the steering wheel. Is there too much free play? Too much play happens when you turn the steering wheel, yet the truck does not steer. Do you feel a sticking or binding when you turn the wheel? You might simply need to add power steering fluid. Another possibility is a power steering fluid leak or problems with the power steering pump.
Check power steering pump, mounting, and hoses. Are there leaks, cracks or bends? Make sure the pump is properly secured.
Check power steering fluid. The color should be clear, pink or red. A black or dark brown color is a sign of contaminated fluid. Top off fluid level according to factory specs.
Check steering gear. Is the gear securely attached? Are there leaks?
Inspect steering shaft U-joints, pinch bolts, splines, pitman arm-to-steering sector shaft, tie rod ends, and linkages. Do you notice wear and tear?
Check kingpins. Are they worn?
Check wheel bearings. Are they loose? Noisy?
Check non-drive hubs: Check oil level and condition of all. Are there leaks?
Check springs, pins, hangers, shackles, spring U-bolts, and insulators. Inspect for wear and tear.
Check shock absorbers. Are the shocks securely attached? Are there leaks?
Check air suspension springs, mounts, hoses, valves, linkage, and fittings. Make sure there are no leaks or damage.
Check suspension ride height. Write down your findings.
Check axle locating components (radius, torque, and/or track rods)
Check front axles and attaching hardware for wear and tear.
Check kingpins, steering knuckle bushings, locks, bearings, seals, and covers for wear and tear.
Check shock absorbers, bushings, brackets, and mounts, which should be solid and free of wear and tear.
Check leaf springs, center bolts, clips, pins and bushings, shackles, U-bolts, insulators, brackets, and mounts for wear and tear.
Check axle aligning devices such as radius rods, track bars, stabilizer bars, torque arms, related bushings, mounts, shims, and cams.
Check condition of tandem suspension equalizer parts.
Inspect and test air suspension pressure regulator and height control valves, lines, hoses, dump valves, and fittings
Inspect air springs, mounting plates, springs, suspension arms, and bushings
Brakes are your vehicle’s most important safety system since they control slowing and stopping. We will focus on hydraulic and air brakes.
Hydraulic Brakes
Hydraulic brakes use the properties of liquid—brake fluid—to transfer the brake pedal movement to the wheels and slow or stop your vehicle.
When you press the brake, does the truck slow but not stop the right way and roll a bit? This could be caused by low brake fluid, a leaky master cylinder, air in the hydraulic system, worn brake pads or shoes.
Does the brake pedal feel soft instead of firm? You may have a leak in your brake line. You may have air in the system (your brakes may need to be bled). The brake fluid may be contaminated. Maybe the prior owner is not using the right type of brake fluid.
Does the brake pedal vibrate? The brake rotors/drums may be warped. The tires could be out of balance or worn out. The front wheel bearings might be loose or worn out.
Some basics to check:
Test the anti-lock brake system warning light operation (includes trailer and dash-mounted trailer anti-lock brake warning light).
Test the anti-lock brake system electronic control and components. Self-diagnose or use electronic/scan tools to diagnose.
Check for poor stopping and problems with wheel lock-up. You should not have these problems if the anti-lock brake system is functioning properly.
Check the operation of anti-lock brake system air, hydraulic, electrical, and mechanical parts
Check anti-lock braking system wheel speed sensors and circuits
Check the operation of the automatic traction control (ATC) warning light
Check operation of the power line carrier (PLC)
Learn more about hydraulic brakes
Air Brakes
Air brakes don’t work instantly like hydraulic brakes. Air needs to flow through your brake lines before you can brake. Water in your air brake system can cause serious trouble; in cold weather, that water can turn to ice and block air from passing into the brake lines. This could cause your wheels to lock up.
Basics to check:
Check for poor stopping, early wear, air leaks, pulling, grabbing, or balance problems.
Drain air reservoir/tanks; check for oil, water, and dirt/foreign objects.
Check air compressor drive gear, belts and coupling.
Check air compressor inlet; inspect oil supply and coolant lines, mounting brackets, and fittings
Check air system pressure controls; governor, unloader assembly valves, filters, hoses, lines, and fittings
Check air system lines, hoses, fittings, and couplings
From headlights to reflectors and turn signals, you need to see and be seen to operate your heavy-duty truck legally and safely. The basics:
Make sure all required lights are working properly.
- Are headlights brighter than normal?
- Are headlights intermittent, dim, or not working?
Wiring problems can cause lights to malfunction. For example, the lights might stop working when you hit a bump in the road. A bad connection or bad wire can be the culprit.
Check lights by walking around the perimeter of the truck and trailer to check the lights and their functions:
- In front and rear of the truck
- On both sides of the truck
- On both sides of the trailer
- In rear of the trailer
Test the following functions:
- Left Turn Signal
- Right Turn Signal
- Four Way Flashers
- High Beams and Low Beams
- Brake Lights
Make sure that Lights, Reflectors, & Reflective Tape are:
- Properly mounted and secure
- Not cracked, bent, broken
- Clean and illuminated
- The proper color of amber to the front and sides, and red to the rear.
- Turn on your marker lights and headlights
The care of wheels and tires is essential to the safe operation of a heavy-duty truck. When neglected, you face poor handling at best to blowouts and accidents at worst.
Do all tires match in diameter and tread? Mismatches in tires cause more wear and tear on your drive train.
Check tires for proper mounting. Improper mounting adversely affects wear patterns.
Check the tread depth of each tire with a gauge and compare with new tire specs. You’ll then know how much tread is left in your tires. Uneven tire wear could mean an axle misalignment.
Check tires for cuts, cracks, bulges in the sidewall. Such insults can be caused by impact, overloading, or driving with underinflated tires.
Check tire air pressures; adjust specs according to manufacturer
Check condition of wheel mounting hardware. Do you see cracks? Are any parts loose?
Check condition of wheels. Do you see cracks or damage? Are wheels properly aligned?
Check wheel lug nuts and bolts. Are any nuts or bolts missing?
Check condition of valve caps and stems. Are any caps missing? The caps keep dirt and debris from the stems; if enough dirt works its way in, your tires could lose air.
When you realize we have not even begun to discuss all of the systems you’ll need to inspect, you might be overwhelmed. While you might choose to perform your own cursory heavy duty truck inspection, your safest best is to get a professional mechanic to inspect your vehicle. A pro will catch anything you may miss-and spare you the headaches of buying a lemon. Plus, you’ll have more power at the negotiating table when a professional mechanic inspects your vehicle and lists the problems that need attention.
Let Vancouver Axle and Frame perform your vehicle inspection for you. We are an ICBC Designated Inspection Facility. Contact us today to schedule your inspection or call today to set up your inspection appointment at (604) 882-5113