Cummins 8.9 ISL Problems, Reviews, and Life Expectancy
Good engines are hard to find. Just when you think you have the best engine possible, it starts to fail on you. No matter how good an engine is, it is only as good as its weakest part. That weak part may not be where you think it is. Sometimes it involves the transmission.
On some ISL engines, it seems that the TCM or transmission Control module needs to give the ECM permission to start. If that part fails, you won’t be starting the engine any time soon. The fix is to replace the TCM through an Allison dealer.
To learn more about this engine, just continue to read our article. It has the information you want to know about so you can get to the heart of the problem quicker and hopefully cheaper. Some repairs can cost thousands of dollars.
List Of Cummins 8.9 ISL Problems
Many RV owners have individual problems that others may not experience. For example, the non-start problem can be the starter, it can be the ECM or it can be the TCM. Finding the source can be difficult when there are multiple possibilities as well as multiple symptoms for the same problem.
Some fixes are easy, for example, sometimes all you need is a software update and everything will work fine. Other times, it is not so easy as parts need to be replaced or repaired. That can cost a lot of money. Here is a list of common problems you may experience with this engine:
Camshaft Failure - check to see if the gear is broken and replace if it is damaged. Then replace the camshaft if it is damaged
Crankshaft Failure - replace the crankshaft
Lifter/Roller Failure - replace the failed parts
Connecting Rod Failure - this could lead to an engine replacement.
Spun Crankshaft Bearings - when this happens, you may have to replace the whole engine as the possibility of the block and crankshaft being damaged beyond repair is great.
Cracked Cylinder Head(s) - this may need some furnace welding, then surfaced again to have them work right
Scored Pistons and Liners - Re-machining the pistons should be the best repair but the liners should be replaced
Over Fueling - the Electronic Fuel Control Actuator may have failed on you and it will cost roughly 4300 to get one
Lack of oil or oil pressure - the lack of oil is easy to fix, just add more. For the lack of oil pressure, you may need to replace your oil pump
Extreme Blow By - there are about 10 sources for this problem. To get you started you may have to replace the crankcase ventilation filter or you need to replace the crankcase ventilation valve
Dropped Valves - need to be taken to an approved Cummins dealer or mechanic for repair or replacement
Water pump fails - replace the water pump and see if that solves the problem for you
Turbo hose falls off - either re-attach it yourself or have an experienced mechanic re-attach or replace it.
EGR cooler breaks - should only happen on pre-2014 engine models. Replacement is the only solution here.
Cummins ISL 8.9 Reviews
There are not a lot of reviews on this motor. One engine repair and installation company did not have anything bad to say about this motor. They are not recommending that you scrap this motor and replace it with another model.
Then we checked several RV discussion forums to see what actual owners had to say. Not one had anything really negative to say about this engine. They may not have liked the problems that have come with it but many of these owners have not experienced those problems yet.
If anyone had a problem it is with Cummins customer service and the fact that many of their mechanics do not understand why a part failed. Some people are certainly not happy with the company even though they were happy with the motor until they had a problem or two.
This engine does not have any review websites stating it is a terrible motor. As we said, most owners are happy with the performance when it works right. If you do a search, you will find quite a few of these used engines for sale.
If they were bad, no one would sell them except for a scam artist. The reviews look good for this motor and you should be able to get a lot of miles on it before you face any of the above problems.
There are a few lemons in the group and one engine blew a rod at 27,000 miles approx. The rod was machined wrong which is why it blew. But if you are outside your warranty period, do not expect Cummins to be of much help.
Cummins 8.9 ISL Life Expectancy
While not stated specifically on any website we could find, a used engine was being sold with over 550,000 miles on it. That should give you a clue as to the lifespan of the motor.
You can plan on at least 500,000 for the B50 rating. At that point, 50% of these engines may need an overhaul. But you may get lucky and go further before needing that repair.
The key is going to be how well you maintain the engine and how hard you drive it. Heavy-duty service will take its toll on any engine and if you are a hard driver, then do not expect the engine to last up to 500,000 miles before needing repair work done.
Then if you do not maintain it, you may lose your warranty from Cummins. To remain in compliance with the warranty, you have to change the oil at least once a year. Failure to do that may void your warranty.
The company calls for at least 1 oil change per year for this motor. Or 20,000 miles, whichever is first. The engine’s lifespan will be determined more by how you look after it than by any part that may fail.
Cummins RV Engine Problems
One problem was with starting. One owner was able to start his engine for the warm-up session but then after turning it off, he could not start it again. He just got a clicking noise.
While most other owners responding to him thought it was the starter or ECM, it turned out to be the TCM. Similar problems required an update to the software on the engine and it started up just fine.
A known RV problem is the EGR cooler. It does fail on many occasions and the only repair that can be made is to replace it with the updated ISX cooler and an adapter kit.
However, the cost of this repair can run around $4500. The EGR was in use on the pre-2014 ISL engine models. They are no longer made or sold by Cummins.
Next up will be the water pump. It can fail on you at different times. The repair for this problem is a replacement pump. Filters are going to be a common problem on RVs.
You will need to change the filters regularly, especially the fuel filter as you do not want any debris or particulates entering the fuel system. When it does, those pieces can alter the spray to a point where it creates a hole in the piston top or cylinder wall.
Do not forget to change the air filter roughly every 7,000 miles. The filters will need to be changed more often than the oil or coolant. Keeping them in shape will protect your engine.
Cummins ISL 8.9 Fault Codes
We can’t list them all here as the list is quite long. But there are enough placed here to give you an idea of what to look for when you see these fault codes appear.
Fault Code 111
Electronic Control Module Critical Internal Failure. Bad Intelligent Device or Component.
Fault Code 115
Engine Magnetic Speed/Position Lost Both of Two Signals – Data Erratic, Intermittent, or Incorrect.
Fault Code 122
Intake Manifold 1 Pressure Sensor Circuit – Voltage Above Normal or Shorted to High Source.
Fault Code 123
Intake Manifold 1 Pressure Sensor Circuit – Voltage Below Normal or Shorted to Low Source.
Fault Code 124
Intake Manifold 1 Pressure – Data Valid but Above Normal Operational Range – Moderately Severe Level.
Fault Code 131
Accelerator Pedal or Lever Position Sensor 1 Circuit – Voltage Above Normal or Shorted to High Source.
Fault Code 132
Accelerator Pedal or Lever Position Sensor 1 Circuit – Voltage Below Normal or Shorted to Low Source.
Fault Code 133
Remote Accelerator Pedal or Lever Position 1 Circuit – Voltage Above Normal or Shorted to High Source.
You can find the rest at this link.
Some Final Words
According to some mechanics and owners, this is the best-designed diesel engine that Cummins has made. You should get between 400,000 and 500,000 miles on it before any seriously goes wrong.
It doesn’t always happen that way so be prepared and have some cash reserves to cover the costs of repairs or an extended warranty to protect you.
