Are Cummins Engines Reliable? (9 Cummins RV Engine Problems)
When you specialize you can become a master of your chosen field. Being a jack of all trades may bring versatility but it does not bring mastery of all trades. Cummins specializes in diesel engines and they have become the master of that engine type.
Are Cummins engines reliable? For the most part, Cummins’ diesel engines are the most reliable motors you can have powering your RV. They usually last over 1,000,000 miles on regular maintenance. However, the new smog devices seem to be the cause of many of the engine’s troubles.
To learn more about Cummins and their reliable motors, just continue to read our article. It explores the issue so you can make an informed choice on purchasing a rig with that engine in it or not. Take a few minutes and see how reliable these motors are.
A Fine Heritage
The company was started by a young farm boy who hated farm work. His goal was to make that work less boring and easier to do. His name was Clessie Cummins and he had a talent for engineering, not farm work.
This young man proved his engineering talent when he was a mechanic on Ray Harroun’s racing team. Mr. Harroun was the first winner of the Indy 500 in 1911. 41 years later Mr. Cummins took an Indy race car to the pole powered by his diesel engine.
Mr. Cummins was a true engineer and motor maverick, his achievements prove that true. Originally designed as an agricultural motor, the Cummins engineering spirit has led to the development of several diesel engines that are found in school buses, fire trucks, container trucks, and more.
Today, the Cummings company employs over 34,000 workers in roughly 200 countries of the world simply because it is a great motor built on the shoulders of previous reliable engines.
Not everything is perfect for Cummins as some engines they have produced are not as reliable as others. Some need an overhaul at 500,000 miles while others will last double that amount before needing a major repair.
Sometimes, it is just the luck of the draw when your rig gets a lemon and you do not get the expected longevity or performance Cummins engines are known to produce.
Are Cummins Engines Reliable?
For the most part, the answer will be yes to that question. Cummins’ motors are known for being very reliable, powerful and produce a lot of torque so you can haul your RV anywhere you want.
But there is a qualification to that statement. The overall reliability will depend on the year the motor was made. For example, the original C Series ISC 8.3 motors were a simpler more mechanical engine that had fewer parts to worry about.
Those motors are considered very reliable but the new models come with a lot of updates that were designed to improve power, torque, and performance. However, the original motors are seen as more reliable than the newer ones.
The 6.7 engines are said to be one of the most reliable motors around but that is if you delete some of the added smog control devices from your motor. One owner said he deleted some of those controls and had 3/4 of a million miles trouble-free.
Just so you know, deleting smog control devices are illegal and your dealer will find those deletions. When they do, they can void part or all of your warranty. Then for the B series, the original 5.9 engine is supposed to be very reliable but that was before any smog or emission control devices were added.
Common Cummins RV Engine Problems
You may have guessed already what one of the most common Cummins RV engine problem sources is. The many anti-smog or anti-emission devices placed on those engines used in powering RVs.
Those devices seem to hamper performance and make the engine a bit weaker so owners do not get the longevity or reliability they have heard about. This is a common complaint with many regular car owners as well.
Another issue that may be common with the B series 24 valve and electronic fuel injection engines is that the injection pump often failed and the valve seats cracked. The 3rd generation 6.7 had issues with the variable geometry turbo as well as the emissions equipment.
Other common problems are not related to the motor but to the size of the pick-up truck, it is put into. Dodge Ram trucks have gotten larger over the years making them too pick for traditional parking spaces and too tall to go into parking garages.
Then the stiffer springs provided a rougher ride even though the diesel motor runs smoother than a gas-powered one. One thing that made the 1989 to 1994 Cummins Ram motors more reliable was that they did not contain glow plugs.
Their turbo and direct injection design made those obsolete and the engine was far more reliable. When Cummins switched from the P Pump to a new system, many RV owners had problems with the new system.
Then the off-road heavy-duty trucks often endure the most problems than the RV motors. These engines can suffer from block problems. The 8.3L will experience valve dropping, while the 8.3ISC has the P-pump replacement issues. That replacement is called CAPS and can be also be found on the 5.9 engine.
What causes those problems is usually too much water in the fuel and very high heat levels. Most of the time you may experience individual issues that do not happen to other RV owners.
One owner had trouble with his 2007 ISX 650 CM871 engine as it blew twice before it even reached 50,000. That owner has had nothing but problems with his engine as valves broke, the turbo malfunctioned, the head, liners, pistons all were damaged and needed replacing.
However, another owner did not experience that same issue.
Cummins RV Engine Service
It does seem that Cummins cares about its RV customers. They have had a Coach Care service in place for some time and recently, they have declared it is improved. The upgrade is including chassis and major systems services in their service plans.
The chassis service is supposed to be complete and you can get it not only at the regular Cummins dealers but you can find the service at 60 Spartan locations as well as selected Tiffin outlets. The company offers 2 plans for this Coach Care service.
The cheaper plan goes for $329 and includes a 64 point chassis inspection as well as inspections on brakes, fluid levels, tires, air & fuel systems, and more. They also look at the engine compartment and the external lighting and alarm functions.
The more expensive service runs you $1,250 and includes different oil changes along with filters etc. There are also different groups you can belong to that help you get discounts on the costs of approved repairs.
The one we saw was RVGEEKs and it may help you get lower prices on the two above Coach Care packages. You would have to use those letters as your discount code to get the lower prices.
Cummins ISL9 Problems
This engine is said to be one of the finest diesel engines you can buy today. It has been a top performer for at least 15 years but despite its top reputation, it still has a few problems.
Up to 400,000 miles, you should experience relatively few issues as long as you do regular maintenance. Some people think the once-a-year maintenance routine is too much of a gap and opt for more reasonable maintenance schedules.
Those are either every 7,000 miles or every 8 to 10,000 miles. The choice is yours but it seems that the more maintenance you do each year the better the engine performs overall.
Between 400,000 to 500,000 miles it is said you may have to overhaul this motor. That is when the real issues kick in. One example would be the EGR cooler will go out on you. Then the water pump can malfunction as well.
Also, people are pointing to the emission control devices that are the cause of many of their issues. They say that those devices are hard on fluids breaking them down faster. That is one reason they decided to go with more frequent fluid changes. One final place to watch would be your filters, they may not last that long anymore.
Cummins RV Engine Warranty
It is possible that you may have to deal with two different warranties on your RV. if your rig is made by Freightliner, you may have a Freightliner-Cummins warranty or just a Cummins warranty. We found both but it seems certain websites are down and specific information is impossible to get at this time.
However, the warranty you get will have depended on the year the engine was built and the model. A basic standard guarantee from this company is 100,000 miles or 5 years for the engine.
To get information on their extended warranty plan you have to enter your engine serial number in a box on their support website. You should go to their website directly to get the information you need direct from the horse’s mouth.
Here is the link to their warranty support page and keep in mind the limited warranty issued for the Cummins product you purchase is restricted to that product only. Another reminder is that Cummins only guarantees those parts that fail due to their negligence or poor craftsmanship.
They won’t cover any part that failed due to negligence, etc., on your part.
What do Cummins ISL9 Reviews Say?
Most of the reviews that we saw spoke very highly of this engine. One reviewer pointed to what statistics have shown and that it is one of the best-designed engines you can buy.
Another said that their model from the pre-emissions era or the beginning of that era was far better than the models that had a lot of emission control devices added to them years later. A self-reporting mechanic claims that the ISL9 is one of the finest engines he has worked on in 25 years of working as a mechanic.
Then another reviewer has stated that it is probably the best diesel engine on the market and has been since it was introduced 17 years ago approx. Others have said the same thing. However, one owner has had the bad luck of the draw as he seems to have some issues with the engine other owners do not have.
He wasn’t negative in his review just reporting what he experienced. That is the way it is with the reviews. Most people we saw were positive and filled with high praise for this motor.
A Word About Deletion
This is a common discussion topic when it comes to Cummins and other diesel engines. The owners of these motors often participate in this practice without Cummins or the dealerships knowing about it.
Deletion is the practice of removing emission control devices from your diesel engine to make overall engine performance better. This practice is highly illegal and the dealer may void your warranty if they find out about it.
However, the benefits convince many RV owners to do this, and here is what you get when you do delete emission control devices:
- Improved performance
- Better sound
- Improved reliability
- Improved fuel economy
- Fewer repairs
If you do this, this is all on you as we do not recommend breaking the law or voiding your warranty.
Some Final Words
As you can see Cummins has a long proud heritage standing behind the engines they make. This company makes very reliable motors that often outlive the RV rig they are placed in. That is a good sign when you spend a lot of money on an RV.
