As diesel engines age, owners often face the question: Is it worth overhauling my diesel engine, or should I just replace it?
This is a fairly straightforward decision if you have considered all of the variables such as the condition of the engine, the cost of the overhaul, the potential value of the vehicle, any planned performance upgrades, and warranties.
In the article, we will have an in-depth look at each variable, as well as provide some tips on how to maximize the life of your rebuilt diesel engine.
Key Takeaways:
– Rebuilding your diesel engine is more cost-effective than replacing it.
– Replacing your diesel engine is a better option if you’ve suffered catastrophic damage.
– Expect 150,000 to 300,000 miles from a rebuilt diesel engine.
Introduction to overhauling diesel engines
Overhauling a diesel engine is synonymous with rebuilding a diesel engine. The process involves disassembling the engine so that major components such as piston rings, valves, and bearings can be cleaned and inspected. Components that are found to be worn out can then be either machined or replaced.
A diesel engine overhaul is typically only considered when performance issues are detected. These “performance issues” may include:
- decreased fuel efficiency
- Reduced performance and power
- Increased exhaust emissions
- Engine warning lights or codes.
Your mechanic will also use additional diagnostic tools such as a compression test or oil analysis to determine if it’s time for an overhaul.
Is it Worth Rebuilding a Diesel Engine?
Below is a look at the most important variables to consider when deciding between an engine rebuild vs an engine replacement.
What is the condition of your diesel engine?
It’s my opinion that the first thing you should ask yourself when considering rebuilding your diesel engine is, what is its current condition?
To assess this, you can start by asking yourself why you want to rebuild your engine in the first place. Did you suffer a catastrophic failure such as engine seizure? Or did you maintain your engine well for a decade, and now it’s slowly losing performance?
If you experienced a sudden catastrophic failure, it’s very likely that you will have major structural damage to the engine. For example, if you have cracked your engine block, scored your cylinders, or broken connecting rods, you are better off replacing the engine outright.
Here is the reason for my answer: after a catastrophic diesel engine failure, it’s possible that you will not be able to machine the block back into tolerance during a rebuild.
And second, the structural damage to the engine is likely widespread. It also may have caused collateral damage that is hard to identify and may get missed on a rebuild.
On the other hand, engines that are well-maintained and have fewer than 400,000 miles are good candidates for rebuilding because we would not ordinarily expect “structural damage”.
These engines normally only need to be cleaned, inspected, and have common wear items replaced (compression rings and bearings etc.). The likelihood of finding irreparable damage is much lower.
Rebuilding vs Replacing Cost Analysis
Doing a basic cost comparison of rebuilding versus replacing a diesel engine can help guide your decision-making. I’ve provided an example of this below.
Option 1: Rebuild
When you decide to rebuild your diesel engine, you’ll need to begin by purchasing a diesel overhaul kit for your make and model.
For example, at the time of writing this, a rebuild kit on eBay for a 2006 Ford 6.0L V8 Powerstroke diesel costs around $1250. The kit includes all the standard wear items such as gaskets, pistons, piston rings, crankshaft bearings, connecting rod bearings, camshaft bearings, seals, and plugs.
The second component is the labor cost involved.
The average diesel mechanic charges $120/hour, but this varies by location. You may also consider using a different value if you are performing the labor yourself.
From my experience, the average time to rebuild a diesel engine is about 20 to 40 hours of labor. We will assume 30 hours for our example. So, for our 2006 Powerstroke rebuild, our costs are:
Rebuild kit: $1250
Labor: $3600 ($120/hour times 30 hours)
Total: $4850
Option 2: Replace
“Long Block” Definition: An engine that contains essential components such as the cylinder block, cylinder heads, crankshaft, connecting rods, pistons, and camshaft. A long block typically does not include external components such as the starter, alternator, exhaust/intake manifolds, etc.
Sticking with our 2006 Ford 6.0L example, we can easily source a rebuilt engine for $5395. This comes with all new internal components.
The labor to remove the old engine, swap components onto the long block, and reinstall the new engine is on average around 15 hours.
Keeping with our assumed $120/hour shop rate, the cost breakdown to replace our example diesel engine is:
Long Block Replacement: $5395
Labor: $1800 ($120/hour times 15 hours)
Total: $7195
Rebuild vs replace cost comparison
You can expect at least 150,000 miles out of a new or rebuilt engine with proper maintenance. For the average American, this is about 10 years of driving.
This means that our cost of rebuilding our engine is roughly $485 per year, or just over 3 cents per mile.
The cost of replacing our diesel engine is roughly $719 per year or about 4.8 cents per mile.
The result, unsurprisingly, is that it’s about 35% cheaper to rebuild your diesel engine rather than to replace it.
This is one more reason why maintenance and care throughout the life of your vehicle are so important.
Rebuild/repair VS buying a new vehicle
Often, when it comes time to rebuild or replace your truck’s engine, many owners will opt to just buy a new truck and start again from the beginning.
A midmodel Ford F250 currently costs around $65,000 new and can be expected to get around 200,000 miles, or 13 years of driving out of it.
This breaks down to $5,000 per year or around 32 cents per mile.
With that said, both rebuilding or replacing your engine is 85% to 90% cheaper than replacing your vehicle with a new model.
This math, of course, ignores warranties and other components; however, I do not believe you can fully make up the cost difference.
Potential Value of the repaired vehicle
Whether you rebuild or replace your diesel engine, it will have the same effect on the potential value of your vehicle.
“Potential Value” Definition: The price you would theoretically receive by selling the vehicle.
I’ve taken the average of 7 2006 Ford F250 6.0L trucks on the used market with mileage that would indicate that they might be getting close to needing an engine overhaul (More than 200,000 miles and being sold “As Is”).
The average asking price came to $9,227.
Sticking with the same year, make, and model, I scoured the internet for the same trucks with either a rebuilt/overhauled engine or, at minimum, with less than 40,000 miles.
I was only able to find 4, but the average asking price was $15,555.
This suggests that it might be possible to recover the cost of a rebuild through the appreciation of the vehicle’s potential value.
However, it does not appear likely that you would be able to recover the price of replacing an engine. The potential value of the vehicle does not increase to the point of recovering your costs.
Rebuild Vs Replace: Performance Upgrades
Deciding early on that you want to improve the future performance of your engine in some way will play a key role in deciding if you should rebuild or replace your engine.
For example, you might decide that you want your new engine to have a higher compression ratio to increase performance. You might try to achieve this by using a piston with a higher compression height, which doesn’t come standard with your prebuilt long block.
In this case, your best option is going to be to rebuild the engine rather than replace it.
Rebuild Vs Replace: Warranties
Finally, we come down to warranties.
Starting with rebuilding, the warranty process is going to be much less clear and deserves more attention.
Often, the components in your rebuild kit will have a one-year warranty, but this will only be for parts and not for labor. Be sure to ask your mechanic and machine shop if they warranty their work as well.
The warranty of a replacement long block varies by manufacturer and supplier, but they will normally have a one-year 12,000-mile warranty.
These warranties will often not cover improper installation, so you still need to check with your local mechanic on their policies.
Overall, you are often going to have the best warranty coverage by replacing your engine.
Maximizing the Life of Your Rebuilt Diesel Engine
Rebuilt diesel engine longevity depends entirely on how you maintain it. Here are some tips to follow:
- Follow the recommended maintenance schedule: Regular oil changes, filter replacements, and fluid flushes will help maintain the health of your engine and extend its lifespan.
- Avoid overloading your engine: Overloading your engine can cause excessive wear and tear and can even cause it to fail. Make sure you don’t exceed the maximum weight recommended for your vehicle.
- Use quality parts: Using quality parts, such as OEM parts or high-quality aftermarket parts, will ensure your engine runs smoothly and lasts longer.
- Monitor engine performance: Regularly monitoring engine performance and addressing any issues as soon as they arise will help prevent major problems down the road.
- Drive smart: Aggressive driving and excessive idling can shorten the life of your engine, so take it easy on the accelerator and avoid long periods of idling.
How long will an rebuilt diesel engine last?
Normally, a rebuilt engine will likely last as long as a brand-new engine, but there are no guarantees.
The lifespan of a rebuilt engine depends on many factors, including the quality of the parts used, the skill of the mechanic, and how well the engine is maintained.
On average, a rebuilt diesel engine can last between 150,000 to 300,000 miles, but it’s not uncommon for engines to last even longer.
Conclusion
After considering all of the variables, it’s my opinion that rebuilding your diesel engine is a better choice than replacing it, as long as you didn’t suffer catastrophic damage.
Be sure to take any future performance upgrades into consideration when deciding for yourself, and carefully read and discuss warranty documents with your dealers and mechanics.