Is The Cat C7 a Good Engine? Problems, Reviews, Reliability
It is okay to be worried. Everyone hears the horror stories about the C7 engine made by Caterpillar. These stories are few in number. What people do not factor in are the thousands they do not hear about who have had no problems with their C7 engine.
The C7 was supposed to be the golden child from Caterpillar and a top engine. However, its production run lasted only 6 years between the years 2003 and 2009. This engine was made to meet the Tier 4 emissions requirements but it may not have lived up to that purpose.
To learn whether or not the C7 is a good engine, just continue to read our article. It has the information you want to know about so you can decide if you want to risk buying a used RV with that motor under the hood or not. It is not as bad as some people think.
Is The Caterpillar C7 a Good Engine?
On paper, this engine looks pretty good. It was offered with 8 HP ratings from 210 to 360 and several torque levels, from 520 to 925 lb-ft. This was an inline 6 that was made for heavy vehicles weighing up to 33,000 pounds. RVs and skoolies were two of the main vehicles this engine was put in.
Then this motor was the replacement for the 3126 and it shared many design features like the engine configuration. It also had the same bore and stroke as the 3126, 4.330 & 5.000. So expectations were high for this new motor.
This engine was also filled with innovations in the engine industry like the HEUI injector system, the ACERT or Advanced Combustion Emissions Reduction Technology, and upgraded ECM.
You could say that it was a good engine and many RV owners have had no complaints. Probably more than those that had complaints but it is hard to say as the former group does not usually report their good fortune.
What stopped production was not the many problems this engine had but the fact that Caterpillar got out of the on-road heavy/super-duty class market. The reason that forced this move was the fact that they would have to spend a lot more money to meet the upcoming 2010 emission regulations.
It was a good business decision as these emission regulations change all the time and it can cost a company millions just to meet them. It was just not a good way to spend money.
2005-2007 Cat C7 Engine Problems
One of the main areas that created problems for Caterpillar and this engine was the switch to Ultra Low Sulfur Diesel or ULSD. This fuel is very hard on different diesel engine components.
It is thinner and has lower lubricity which dictated a change to the ACERT fuel system. That system had to change to a common rail injection system. This meant that the PSI for the injectors and the fuel pump went up to extreme levels.
In the end, the ACERT technology started to have problems like clogged diesel particulate filters, as well as clogging of the turbocharger inlet. Other problems include but are not limited to the following:
1. Overheating- the engine had to run hotter to burn off diesel particulate matter. So far not so bad but the cooling fan did not turn on till 235 degrees F and that could cause overheating.
Drivers were told to downshift going up hills and not go above 1100 RPM to avoid any overheating issues. This problem also put a strain on the coolant system which drained the coolant to dangerous levels.
2. Engine oil- the C7 burned a lot of oil over time and one possible source was an injector seal issue. There were also problems with keeping the oil pressure at safe levels.
Any knocking heard by drivers usually meant there was not enough oil in the oil pan or circulating through the engine.
3. Valves- Caterpillar used injection actuation pressure control valves (IAPCV) and pressure relief valves. These parts may not have been machined properly as they were known to fail frequently.
Valve drop was another problem that came with this motor. But those were usually found in engines that were installed in heavy-duty vehicles.
4. Misc.- there were other problems that some owners faced. They may not have been faced by them all but they did appear from time to time. Those problems were- cracked cylinder heads, crankshaft failures, and connecting rod failures.
Cat C7 Engine Reliability
One observation stated that the pre-2006 motor was very reliable as long as the valves were adjusted and adjusted on schedule. After 2006, it was not a very reliable motor to have.
Part of that change may be due to the fact that the government changed the diesel fuel requirements and made it an ultra low sulfur diesel variety. This is a big change as in 1994 the parts per million (ppm), went from 600 to only 500.
But new regulations that came into effect for diesel fuel around 2004 to 2006 required that diesel emissions had to be cut drastically. One way this was done was to drop the sulfur ppm from 500 to 15.
This created a major problem as diesel fuel lost its lubrication power. Many engine makers had trouble meeting these new standards as the low lubricity of the fuel caused a lot of internal damage to motors.
Which is while that observer could make that remark. It was difficult for diesel engine builders to overcome the problems created by ULSD. The life expectancy of this engine was around 450,000 to 500,000 miles.
This was double what the 3126 and the 3116 got. So in terms of longevity, it was a nicer motor if you did not drive it for long stretches every year and reached that mark quickly.
But with the proper maintenance, it may have been possible to extend that lifespan and put off the engine rebuild for a few more years. This is an important point as an engine is only as reliable as the maintenance it receives.
If you ignore the maintenance and oil changes, then do not expect this motor to be reliable. There are thousands of C7 owners that have found this motor to be very reliable.
Taking those factors into consideration, you can say that the C7 is or was a very reliable motor. Only a few people had problems with it. Those are the people that get the press and report their issues to everyone.
C7 Caterpillar Engine Reviews
There is at least one reviewer that will have nothing to do with Caterpillar or the C7. Not because this engine does have problems but for the fact, they do not like the way Caterpillar does business including customer service.
Other people felt that the C7 was a better engine prior to the ULSD change and did not take into account the problems and challenges Caterpillar had to overcome to make a better motor.
The overwhelming amount of reviews comes from those owners who love their C7 and how it performs. They were almost unanimous in their opinions that they would buy another RV that had a C7 engine under the hood.
One owner reflected that this engine is in buses, fire trucks, and other medium-duty vehicles and if it were a bad engine, they would have been replaced by now. Or they would not have been ordered with that motor.
There were also positive reviews from those owners who experienced some of the problems we listed above. They said that these problems would have come on any engine if they were not properly maintained.
What that means is that they understand that the C7 is not a perfect motor but it did its job well when kept in good shape. That is what you should expect when reading the reviews for this motor.
It will be a mixed batch because either some people did not take care of their engine and were denied warranty protection, or they took care of their engine and received great customer care when something went wrong.
There are a variety of reasons why there are negative reviews and sometimes it is not the engine’s fault. People just want something to complain about. Read those reviews with a grain of salt and keep in mind, their problems probably won’t happen to you.
But if they do, keep an open mind as some problems are beyond the C7’s ability to stop.
Cat C7 Life Expectancy
Engines are measured by a two-category system called the B10 and the B50. The first category indicates how many engines will fail at a certain mileage mark. The 10 stands for 10% of the engines will fail prior to reaching the B50 mile mark.
The 50 in the B50 stands for 50% and it has been estimated that this engine will have a 50% failure rate at the 450,000 to 500,000-mile mark. What that means is that 50% of the owners who bought an RV or truck with this motor will need an overhaul at that mile mark.
The good news is that the other 50% should see far more miles than some of their friends got. This failure rate when compared to other diesel engines is not bad.
The Cummins 5.9 liter has a B50 rating of 350,000 and the Cat 3116 and 3126 were rated at 200,000 miles. Unfortunately, the C7 does not live as long as the Detroit Diesel 60 series motor which has a B50 rating of 1,000,000 miles.
With proper maintenance, you should be in the group that goes past that B50 mark and have your C7 serve you well for many years. You may never see any of these problems if you do not drive your RV that much each year, then trade it in before it hits that B50 mile mark
When it comes to oil maintenance, read our article on the C7 oil capacity. It will fill you in on that aspect of this engine.
Some Of The Top Engines Produced By Caterpillar
This list is subjective and you may not agree with all of the entrants on it. But Caterpillar has had a top reputation for building some very good diesel motors despite some flaws.
1. the 3116- 205hp at around 2,400 rpm and 350hp at 2800 RPM. it is an inline 6 with a 4-stroke cycle with a 4.13-inch bore and a 5.0 stroke
2. C7- you just read about this motor and it has performed well for almost 20 years. Its application goes far beyond the RV industry and has served many owners well over the years.
3. CAT 3408 - a V8, 4-stroke engine that had a displacement of 18 liters. Plus, its ratio was 14.1:1, and produced between 600 & 800 Hp and 2000 lb-ft of torque.
4. CAT C15 - This very reliable engine was first made in 1999 and it replaced the 3406E. A lot of its parts are interchangeable with the 3406E, but it has less oil seepage than its predecessor
5. CAT C16 - this engine shares the same block with the 6NZ but has a longer crank and thinner liners. It is a good workhorse motor but its weakness is the pressure it puts on the oil pumps.
6. CAT C9- This inline 6-cylinder engine started out as an 8.8 liter but was changed to 9.3 in 2007. That year also saw this engine receive the ACERT system. Its production run lasted until 2010.
Some Final Words
Despite what the naysayers claim, the C7 seems to be a very good engine. For most RV Owners it has been very reliable and lasted a long time before they had to overhaul it.
Yes, it has its share of problems but there are thousands of unreported success stories. Just check the maintenance and repair history out before buying. That way you can avoid inheriting other people's problems. Repairs can cost thousands if you are not careful.
