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Common Semi-Truck Problems: 8 Signs Something is Wrong With Your Truck

May 11th, 2022

Greg Wentworth

Greg Wentworth

Greg joined the ATS team in 2019. He’s spent more than 30 years working on all types of trucks and trailers and spent 29 years as a dealer technician. He carries several certifications from different original equipment manufacturers (OEMs). His favorite part of his role as a technical trainer and quality assurance insurance inspector is helping the technicians learn and build their own knowledge base.

Short of an accident, there are few things worse than driving down the road and seeing your check engine light turn on — or any other hazard light for that matter. 

There are thousands of things that could be wrong with your truck, just as there are hundreds of parts on your truck that keep it running. Is it going to be a minor fix? Or is it something that’s going to keep your truck in the shop and off the roads for days? 

I’m the shop trainer and quality insurance inspector over here at Anderson Trucking Service (ATS) and I was a tech for more than 30 years before joining the team. 

I’m going to run through some things you may notice happening with your truck that could be a sign something is going wrong. When you spot the signs in time, you can get your truck into the shop to be serviced as soon as possible (and ideally well before you’re forced to pull over onto the side of the road and wait hours for a tow).

When you’re finished reading this article, you’ll feel much more confident in your ability to spot an impending issue with your truck. 

8 Warning Signs That a Semi-Truck Breakdown is Near

If you notice any of the issues below happening as you’re going down the road, try to get to a safe stopping place to pull over. Don’t ignore these signs. The longer you wait to fix your truck, the worse the problem can become.

Keep in mind that some of these issues can happen without any hazard lights lighting up the dash, so it’s up to you to be mindful of how your truck is running. 

Man driving a semi-truck with his hands on the dash1. It Won’t Start

It’s pretty obvious that if your truck won’t start, something is wrong. Take note of whether your truck is cranking slow, taking a long time to turn over or if it’s not turning over at all. Did the truck do this after sitting for three days without being started? Or did it do this after a 10-hour reset?

Log this information for the shop. It’ll be easier to diagnose if they have information about the conditions in which your truck was slow to start. 

2. Your Fluids are Low

You should regularly check your fluid levels. You could be low on oil, coolant, transmission fluid….the list goes on. If you find that you’re regularly topping off these fluids — more often than you should be — you probably have a leak. 

Look for spots on the ground. Did you leak anywhere? If you notice a spot on the ground after you’ve parked, try to note where it could be coming from. If you have an idea of where the leak is coming from, the shop will know where to start looking. 

3. You Lose Engine Power

Are you noticing that your truck just doesn’t seem to have as much power as it used to? Do you especially notice this when you’re accelerating? You may have a boost leak or a bad sensor. 

Loss of engine power means you could be in an engine derating situation. Engine derating is when the engine’s output is cut back because it’s operating in less-than-ideal circumstances. This could be a sign of something seriously wrong with your truck. Engine derating is designed to preserve your engine’s life until you can get it into the shop.

4. Your Fuel Economy Decreases

There are countless reasons your fuel economy may drop — weather conditions, heavy loads, the roads you’re driving on — but if you see a significant drop, that’s a problem. 

For instance, if you go from getting 7 miles per gallon (mpg) to 5 mpg overnight, it’s time to get your truck checked out. There could be many issues causing the lowered fuel economy.

5. You Can’t Get into Gear  

Do you hear abnormal noises from the transmission when you’re switching gears, moving in forward or reversing? Especially if you hear sounds while reversing, there’s more than likely something wrong with your transmission. 

Are you struggling to get into gear? If you have a manual transmission and you can’t get into gear, there could be a clutch adjustment issue or the clutch brake might not be working. 

6. Your Truck is Shaking or Vibrating

While shakes and vibrations will feel different, both are a sign of a larger problem. 

When your truck is shaking, it’ll feel like driving over rumble strips on the side of the road at 2 mph. You’ll feel the cab shaking up and down. It may have a thumping sound or feeling to it. 

A vibration feels like driving over rumble strips at 65 mph. There’s a buzzing feeling. A shake is much more intense than a vibration.

When you encounter a shake or vibration, you may also notice that your truck is pulling toward the ditch. You may have an issue with your steer tires. Shakes may be a result of a broken internal belt or your air suspension could be going down. 

7. You Hear Weird Sounds 

If you hear weird noises coming from your truck, like knocking sounds or high-pitched whistles, you might have a deeper issue. 

A high-pitched whistle could be a sign of a boost leak. 

8. Your Stack Turns Black

For the most part, trucks since 2007 don’t put out smoke because the diesel particulate filter (DPF) filters it out and limits emissions. You may see steam, but you shouldn’t see smoke. If you do see smoke coming out of your stacks, there’s a problem. 

You could have a breached DPF on your hands. Similarly, if your stacks turn from white or aluminum to black, your filter might be passing soot through. 

Take Detailed Notes if You Spot an Issue

If you notice any of the above signs with your truck, take detailed notes for your shop technician. For instance, having an idea of where a leak might be coming from will help your tech know where to start. Then it’s less of a guessing game for them. 

Taking notes can also prevent misdiagnosis and cut down on the amount of time you’ll spend in the shop. Write down what you’re noticing, when you’re noticing it and how long you’ve been noticing it. 

Front to rear low angle view of shiny red semi-truck.

When is it Time to Pull Over?

You should never ignore a problem with your truck or a warning light on your dash. 

If you’re having issues with drivability, you should pull over in a safe place immediately. If you’re experiencing no issues with driveability, try to instead make it to a good stopping place — whether that’s a truck stop or your final destination. 

If you have a newer truck and your service engine light is on, you should be able to see the error code on your telematics system. Similarly, the road service crew at your company may be able to view the codes on their end. 

Either way, you should call your company or truck dealer to talk through the issue with them to determine the best step moving forward. They can tell you if the code is or isn’t active or if you’re going to run into trouble in the next few miles. Knowing this will help you decide together when you need to get to the shop. 

Get Your Truck In The Shop

Truck breakdowns are an unfortunate inevitability in the trucking industry. And with the current truck and parts shortage, it’s more important than ever that you’re maintaining your truck. That means paying attention to the warning signs that your truck is running in less-than-ideal conditions. Failing to get your truck fixed in a timely manner may only aggravate the problem.

Doing regular pre- and post-trip inspections may help you spot some of these problems early on — such as low fluid levels or low tire pressure — but it’s also important that you get into the shop regularly. 

At ATS, I oversee quality insurance to make sure every truck is being fixed properly so it’ll run efficiently. While there are very minor fixes you may do yourself — like changing out a headlight — you should leave a majority of fixes to the experts. 

Be sure you’re scheduling regular trips to the shop to keep up with preventative maintenance — including changing fluids and checking your brakes and filters — and to catch potential issues before they become major problems that keep you off the road for weeks.