When to Overhaul a Diesel Engine

When to Overhaul a Diesel Engine

The diesel engine is the workhorse of the automotive world. It powers the heaviest loads, from trains to tractor-trailers, and can last for a million miles or more—if properly maintained. Part of that maintenance includes an engine overhaul at some point in every diesel engine’s lifetime, to examine all its components for wear and tear, replace or repair damaged parts, and clean the engine from particle and grease build up. But having your engine overhauled is a costly decision, so it pays to know the right time to do it as well as the consequences of putting it off.

What is a Diesel Engine Overhaul?

A diesel engine overhaul is when a mechanic takes apart an engine and replaces a significant number of engine components in order to restore full power and functionality. The specific parts and amount of replacement varies on a case-by-case basis, depending on whether there has been any kind of engine failure and on the engine’s repair and maintenance history.

In most cases, a diesel engine overhaul requires five basic steps:

Disassembling: Diesel mechanics take apart the upper and lower half of the engine.

Cleaning: Mechanics clean each part of the diesel engine to remove particle build up and make examining each part easier.

Inspecting: Diesel mechanics inspect each engine component to assess its condition and whether or not it needs to be replaced. Typically, an overhaul involves replacing cylinder packs and all associated gaskets. Injectors and the water pump might also need to be replaced, and the mechanic will examine the camshaft, rocker arms, turbocharger, crankshaft and gears for wear.

Repairing: Mechanics repair the parts that can be reused and reassemble the engine with the replacement parts.

Testing: Many diesel engines have a series of factory-approved procedures to test the engine’s power and function.

How Much Does a Diesel Engine Overhaul Cost?

Overhauling a tractor-trailer engine can vary depending on the engine make, overhaul level and the experience of the mechanics performing the work. Typically, certified engine overhauls range anywhere from $20,000 to $40,000. Diesel engine overhauls aren’t cheap, but they do cost a lot less than a new tractor trailer (between $75,000-$180,000). And, unlike an engine failure, you can usually plan for an engine overhaul.

Signs You Should Consider an Overhaul Your Truck Engine

The biggest sign that your tractor trailer needs an engine overhaul can been seen on the odometer. Well-maintained trucks can last up to 1,000,000 miles, but best practice notes that at 700,000 miles or more, a diesel engine should be overhauled. Replacing key parts like a head gasket or injectors can buy you time, but to avoid a catastrophic failure, you need a full engine overhaul.

Some signs you might need an engine overhaul include:

High Blowby: Blowby is the compressed fuel and air mixture that leaks past the piston and into the crankcase. High blowby, where piston and piston ring wear allow excess gases to escape, can cause higher oil consumption. The root causes of high blowby can include turbocharger issues, worn valve guides or cylinder head issues; and diagnosing the problem requires a thorough look at your diesel engine.

Rough Idle: Engines can ‘hunt’ while idling—revving up and down in an attempt to balance fuel and compression or to burn off extra oil from worn components. They can also ‘miss’ during an idle, a.k.a. hesitate, which is usually caused by malfunctioning injector or improper valve clearance. If your tractor trailer has an unusually rough idle, it might be time to examine its engine functionality.

Lower Fuel Economy: A decreasing fuel economy is one of the key indicators you’re losing diesel engine power and functionality. While poor mileage can indicate a lot of things—from issues with your camshaft to contaminated fuel or filter or injector issues—a consistently lower or decreasing fuel economy is a sign that you might want a diesel mechanic to examine your engine.  

High Coolant or Oil Consumption: If your diesel engine is suddenly using up more oil or coolant, it might indicate an oil leak, cracked cylinder head or gasket, or faulty cylinder liners and O-rings. Getting the engine checked can help you avoid an irreparable engine failure caused by overheating. If oil is burning or leaking, it can cause additional problems if not addressed right away, resulting in a more expensive repair.

Blue Smoke: Blue smoke under the hood indicates your engine is burning oil—usually excessive oil on the cylinder wall—along with fuel.  Because the engine components are worn, the clearances can’t fully remove the oil. An engine compression check can help identify where the issue is and whether you need more extensive repair.

Oil Analysis: Many diesel truckers are also turning to analyses that identify high metal concentrations or contaminants in oil to determine when to overhaul an engine. Oil analysis can also identify if unfiltered air has entered the system. Oil analysis works best if it’s done regularly so samples can be compared, and you can monitor how levels rise over time and consider an engine overhaul if they suddenly spike.

Engine Failures an Overhaul Can Fix

It’s always best to opt for an engine overhaul before your engine fails, but—depending on the cause—engine failure doesn’t always mean that you need to purchase a new tractor trailer. There are several instances where parts come loose within the internal engine which require an engine overhaul, but the diesel engine can be repaired:

  1. Spun Bearing: A spun bearing usually seizes itself around the crankshaft, causing damage to the rod journal and the connecting rod. It’s often caused by the strain of high operating loads when your crankcase isn’t significantly lubricated. If the broken rod comes loose inside the engine, it can cause severe damage. It requires an engine overhaul but can be fixed by replacing the broken parts.
  2. Dropped Valve: When a valve head becomes bent and shears, falling into the cylinder, damaging the piston-cylinder-valve system. A diesel mechanic needs to take apart the engine to replace the system, but the engine can run again after the overhaul.
  3. Low/No Oil Pressure: High oil level in the crankcase almost always indicates excess fluid is leaking somewhere else inside the engine. Mechanics must take apart the engine completely to determine the source of the fluid leak.

Engine Failures That an Overhaul Can’t Fix

There are severe consequences to putting off an engine overhaul, ones that completely decommission a diesel engine. While every situation is different, some common engine failures that an overhaul can’t fix include:

Seized Engine: An engine usually seizes because the lubrication system failed, often due to an undiagnosed oil leak. If oil levels get too low, the engine can overheat, melting cylinders or causing a cracked block. A cracked block means you lose nearly all engine power. If any part of the engine begins to melt, warp or crack from overheating it can be impossible to disassemble.

Blown Engine: When a broken timing belt snaps, it ‘blows’ the engine, causing severe damage to valves and pistons. If you’re lucky, the piston will simply hit the valves, and you’ll need a valve repair. But if the piston parts get into the oil pan, they will damage the internal engine components. Too many internal components damaged, and it’s better to start again with a new engine.

Blown Head Gasket: The head gasket’s main job is to maintain combustion pressure in the engine and keep oil and coolant from mixing. When a head gasket blows, oil and coolant leak, sometimes into one another, and the engine overheats. A blown gasket caught early can be fixed, but if the engine overheats too much, it can become irreparably damaged. 

Why You Should Choose an ASE-Certified Shop to Overhaul Your Engine

If a mechanic is going to take apart your truck’s diesel engine and put it back together, your livelihood and safety depend on their expertise. That level of trust requires more than word of mouth recommendations. ASE Certified mechanics undergo extensive testing to demonstrate knowledge of the skills necessary to diagnose, service and repair engines. ASE has a specific series dedicated to Class 4 through Class 8 trucks and tractors, and an even more specified certification for diesel engines within that category.

CDS’s ASE-certified team of diesel mechanics are experts in diagnosing and treating all semitruck automotive issues and conducting extensive repairs and engine overhauls. Equipped with the latest technology in the field, our knowledgeable team has the know-how and the muscle to get your diesel truck fixed the right way and always on the first try— because we believe in quality service that gives our clients peace of mind when they’re out on the road. Contact us at cdspros.com to make an appointment, or stop in our Knoxville location today and we promise that we will have you taken care of and back on the road in no time.

The Details on DOT Inspections

The Details on DOT Inspections

When the time comes for DOT inspections, it can be an anxiety-inducing time for truck drivers everywhere across North America. Though they generally occur during the spring and summer, they can happen at any time during the year or at any place. DOT inspections can determine whether a driver is fit to operate their vehicle and whether or not a commercial vehicle is safe enough to be on the road. Because DOT inspections are rather unpredictable events with extremely high stakes, it’s incredibly vital that all drivers are adequately prepared for them. That’s why we’ve compiled some in-depth information about what DOT inspectors look for during inspections as well as how to best prepare your fleet to pass.

What is a DOT inspection?

As we briefly described above, DOT inspections are a series of roadside tests that determine whether or not large commercial vehicles are in working order. These inspections are often performed by state troopers or inspectors that work for the Federal Motor Carrier Safety Administration (or the FMCSA). Most inspections take place during what is commonly referred to as “DOT week” in which inspectors from the FMCSA work for 72 long hours, investigating almost 65,000 commercial vehicles across the country.

DOT inspections are incredibly important for the safety of everyone on the road, as well as for the operators of the commercial vehicles being inspected. They ensure that fewer accidents or other potentially dangerous roadside incidents take place as the vehicles carry their cargo.

Types of DOT Inspections

There are six levels of DOT inspections that your fleet could be subjected to. We’ve detailed what each level of inspection is looking for, and how to best prepare.

Level 1: The North American Standard Inspection

This is the most comprehensive of all the inspections. Drivers can expect a very thorough inspection of all their documents, as well as the inner workings of the commercial vehicle that they operate. In addition, inspectors also search for drugs, alcohol, and other potentially hazardous material(s).

Drivers should have their driver’s license, daily driver’s log and hours of service, and a driver and vehicle inspection report on hand when they are pulled over for inspection. In addition to this paperwork, the following vehicle mechanisms should be prepared for inspection:

  • Seat belt
  • Coupling devices
  • Brake systems
  • Exhaust and fuel systems
  • Headlamp, tail lamps, stop lamps, and brake lamps
  • Safe loading
  • Securement of cargo
  • Turn signals
  • Windshield wipers
  • Wheels and hubcaps

Level 2: Walk-Around Driver/Vehicle Inspection

This particular level of evaluation is nearly the same as the level one inspection but checks fewer of the commercial vehicle’s mechanisms. It does not require inspecting beneath the CMV, so it is generally less exhaustive than a level one inspection. All the above documents should still be in order.

Level 3: Driver-Only Inspection

As the name indicates, this is an inspection of the driver of a CMV. Inspectors will check for the following paperwork items:

  • Driver’s license
  • Medical card
  • Driver’s daily log
  • Driver incident history
  • Driver and Vehicle Inspection Report
  • Hazmat requirements

In addition to these items, the driver’s seat belt will also be checked for safety insurance.

Level 4: Special Inspection

This level of inspection usually involves the investigation of one particular facet of the truck or commercial vehicle. This usually occurs to either invalidate a previous claim about an aspect of the vehicle or to allow the Department of Transportation to conduct further research about a certain part of the vehicle’s operation. The latter of these options typically occurs when a frequent violation has been discovered, and the DOT wants to track improvement over time.

Level 5: Vehicle-Only Inspection

Level five inspections are similar to a level two inspection and specifically target the safety of the vehicle. The key difference lies in the fact that the driver cannot be present at a level five inspection. These are most commonly performed after an accident or arrest has occurred, in which the driver would already be away from his or her vehicle.

Level 6: Enhanced NAS Inspection for Radioactive Shipments

DOT regulations that came into effect in 2005 require that every commercial vehicle carrying radioactive materials must pass a level six DOT inspection. These include detailed investigations of the following:

  • Inspecting for radiological shipments
  • Enhanced out of service criteria
  • Radiological requirements
  • Enhanced to a level one inspection

Though these requirements for the varying levels of inspection may seem daunting, there are plenty of ways to prepare your personal vehicle or your fleet for a passing grade.

How Best to Prepare for a DOT Inspection

One of the best ways to avoid a safety issue, whether you’re getting inspected or not, is to perform your own walk-around vehicle investigation. Checking the tire pressure of your vehicle, testing your lights, and looking for possible cracks in your windows can be a great start to ensuring that your vehicle passes inspection.

In addition to inspecting your own vehicle and keeping up with regular maintenance, keeping your paperwork in order is also a great way to prepare. Inspectors have a ton of commercial vehicles to check over, so having your licenses and logs organized can make the process move along smoother.

Though you won’t be judged on the cleanliness of your cab, it’s always nice to see that a truck is being taken care of. Cleaning out your cab regularly, as well as washing the exterior of your truck can tell an inspector all that they need to know about how dedicated you are to the job.

Finally, being polite to your inspector when the time comes is key. Inspectors are people too, and they’re only doing their job. Though it can be a frustrating or anxiety-inducing time for a driver, it’s just as stressful for an inspector. Being polite and prepared can definitely affect the results of your inspection in a very positive way.

Even though this is a tedious process, it might be surprising to know that FMCSA inspectors don’t actually want you to fail! We’ve given you a general summary of what occurs during a DOT inspection, but visiting their website can give you all of the answers you need about what inspectors are looking for, and how to prepare.

Certified Diesel Solutions is Here for You

Certified Diesel Solutions has been serving the commercial vehicle communities of Tennessee for over a decade. Our team of expertly trained mechanics can handle any type of repair or maintenance that your automobile or tractor-trailer may require. We offer a range of services including preventative maintenance services, DOT inspections, and detailed fleet record keeping ensuring that your vehicles are working dependably. Our team realizes how important it is to have a team of reliable mechanics that you can trust, which is why we emphasize creating long-lasting bonds with our clients. If you think our services are right for you, we’d love to hear from you! Visit our website or give us a call at (865) 964-6598.

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