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Diesel Truck and Fleet Warning Signs to Look Out For

Truckers drive for hours on end and rack up hundreds of thousands of miles. Commercial truck maintenance is one of the most important parts of your job—especially if you run a fleet—but, still, problems can develop over time. Acting on warning signs can help you avoid painful breakdowns and delays.

Gear Trouble

If a gear sticks, the truck falls out of gear while driving, or the gears are grinding or shaking, have a diesel truck mechanic check it out. It’s not normal for gears to shift when you haven’t made any adjustments to them. Noise from the gearbox can be a sign of trouble as well.

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Dark Transmission Fluid

While transmission fluid is usually bright red, darker fluid often means there’s a problem with the transmission system. The fluid should be checked from time to time. If you suspect something is off, you can tell a lot from how the fluid looks.

Engine Noise

Excessive noise can mean the oil is contaminated or the combustion timing is off. Knocking can be caused by worn or damaged piston skirts, liner seals, or bearings. Have a truck diagnostic run if you hear backfiring, hissing, or spitting or popping sounds.

Burning Smells

If you smell burning, it could be from the transmission fluid or gears grinding together. There could be an electrical problem as well. Never ignore a burning odor, as it could be the precursor to more severe damage or even a fire.

Screeching/Squealing Brakes

It’s not normal for brakes to screech or squeal. The noise might mean it’s time for new brake pads. Not replacing them in time can lead to major brake damage or an accident.

Low Compression

Low cylinder compression can signal poor air filtration, worn piston rings, engine flooding, or timing problems. You might notice a misfire, trouble starting, or a loss of power, as well as reduced gas mileage.


Engines most often overheat due to cooling system problems. You may have a damaged radiator. If you don’t address overheating, additional diesel engine problems will result in very costly repairs.

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Blue Smoke from Engine

Blue smoke is a sign the engine is burning oil. This can occur because of a leak or a worn-out cylinder. The oil chamber may have been filled too high. Blue or black exhaust can warn of engine problems as well.


Vibrations felt through the steering wheel can point to a driveline issue, while those in the chassis can mean you have a tire problem. These sensations may be subtle, but the underlying problem may not be.

Also, if your truck stalls, the engine runs rough, or you see the check engine light, seek vehicle maintenance as soon as possible. Provide as much detail as you can; the most subtle signs can help a technician diagnose the issue. East Coast Diesel LLC has made this easy, as you can always count on our 24-hour diesel mechanic for assistance. We offer a 24/7 emergency mobile truck service. Call 984-209-1766 for immediate help.