The 6 Most Common ISB 6.7 Cummins Engine Problems

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Zach is one of the founders of 8020 Media and a lead writer for DieselIQ. He’s been in the automotive industry for over a decade and has published more than 400 articles for DieselIQ, TuningPro, BMWTuning, & more. His blend of automotive knowledge, writing & research skills, and passion make him an excellent resource for fellow diesel owners. His expertise goes beyond writing and includes a deep knowledge of Cummins and Powerstroke engines, as well as nearly 10 years of DIY experience. Zach is also experienced with tuning and has a wealth of technical knowledge that he brings to every article he writes.

Many also associate the Cummins name with some of the best light truck diesel engines ever. However, no engine is perfect and the 6.7 Cummins diesel is no exception. The 5.9 Cummins legendary reliably unfortunately didn’t translate as well to the redesigned new engine.

The new engine received numerous emissions systems that have ultimately been very problematic since the engines introduction. In this article, we discuss the most common problems on the Dodge Ram 6.7 Cummins engine as well as overall reliability.

6.7 Cummins Engine Problems

  • Clogged DPF
  • Turbo failure
  • Heater grid bolt
  • Head gasket failure
  • Fuel dilution
  • Cracked EGR cooler

Problems with the 6.7 Cummins often come down to emissions parts. However, the turbos and head gaskets are known to run into occasional failures too.

Generally speaking, the reliability rankings are as follow: 2013-2018 models, 2007.5-2012 models, and the 2019-2020 6.7 Cummins comes in last due to the CP4.2 exploding.

Dodge Ram 6.7 Cummins Engine Problems

If you would rather consume this content via a video, check out our 6.7 Cummins Common Problems video below:

1) DPF Clogging

Diesel particulate filter (DPF) clogging is a common problem on the Dodge Ram 6.7 Cummins. Initially, Dodge opted to avoid using diesel exhaust fluid (DEF). Without DEF the B6.7 diesel must run a little bit on the richer side to reduce NOx emissions. This in turn leads to more particulates, also known as diesel soot, which can quickly clog the DPF.

These clogging issues were so problematic early on that Dodge rolled out multiple PCM re-flashes in an attempt to reduce the occurrence. In 2013, Ram pickup trucks receive SCR emissions control systems along with diesel exhaust fluid. This helps reduce particulates, so DPF clogging is less common on the later year 6.7 Cummins. However, it still affects many trucks – especially as mileage builds up.

It’s pretty bad for a turbodiesel engine to run with a highly clogged exhaust DPF. This causes a build-up of back-pressure for the 6.7 Cummins, which can lead to more heat and stress on the engine. As such, it’s important to ensure your 6.7 Cummins DPF is functioning properly. Some have success in washing out clogged diesel particulate filters. Others decide to delete the DPF completely.

Clogged DPF Symptoms

  • Power loss
  • Long crank
  • Reduced power mode
  • Engine fault codes

One of the main symptoms you may notice is power loss on the 6.7 Cummins with a clogged DPF. If exhaust gases can’t escape efficiently you’ll have a build up in pressure. That causes the 6.7 engine and turbo to run poorly. This is especially true if you end up in low power mode due to the 6.7 Cummins DPF clogging. You may also notice long cranks or an engine fault code.

DPF Replacement

The DPF is an expensive piece of emissions equipment. Even a refurbished 6.7 DPF can run north of $1,000 while original filters are nearly double that. Dodge and Ram 6.7 Cummins owners have a few options. Aftermarket higher performance diesel particulate filters exist, but those still often come in over $1,000. Some have success in pressure washing the OEM 6.7 DPF. Trying to clean the filter may not work at all, but if it does it’s likely to be a shorter-term solution.

Ultimately, this leads some to go the route of completely deleting the 6.7 Cummins DPF with an aftermarket exhaust. This is definitely the easiest on the budget and most effective long-term solution. However, DPF deletes do come with some legal concerns due to emissions.

2) Turbocharger Failure

Turbo problems or failures are more common on earlier model 6.7 Cummins engines. However, it can happen on any year as turbochargers naturally take a lot of abuse. We titled this section turbo failure, but there are a few issues that may not result in complete failure. A few issues that may occur with the 6.7 Cummins turbo include:

  • Leaking oil seals
  • Worn bearings (too much shaft play)
  • Sticking VGT parts
  • Compressor or turbine wheel damage

As turbos age, leaking oil seals and worn bearings are among the most common issues. B6.7 Cummins turbos run in excess of 100,000 RPM’s. Over time, the 6.7 turbo bearings may wear down and lead to excessive shaft play. If left alone the turbine or compressor wheel may contact the turbo housing and result in complete failure.

Since turbos run off incredibly hot exhaust gases it’s important to allow the oil to reach operating temperatures before pushing the Dodge Ram 6.7 Cummins too hard. Cold oil splashing on hot turbo seals is a recipe for premature turbo seal problems. You should also let the truck idle for a couple minutes before shutting down the engine. This will help cool the turbo.

Turbo problems can pop up at any point, but it becomes much more common north of 120,000 miles. A turbo rebuild may be possible. However, if your 6.7 Cummins is high mileage on the original turbo it may make sense to replace the entire turbo.

Turbo Failure Symptoms

Look for the following symptoms that may indicate an issue with the B6.7 turbo:

  • Slow spool
  • Poor performance
  • Excessive smoke from exhaust
  • Whining sounds

There are a few other possible symptoms, too. A sudden failure will typically result in drastic amounts of smoke and oil loss. Moderate smoke will also occur when the turbo seals are on their way out. 6.7 Cummins turbos failing over time will generally make whining sounds, spool slowly, and not reach the target boost.

Turbo Replacement Options

New OEM turbochargers come in north of $1,000 and often close to double that price. A remanufactured turbo will run around $1,000 to $1,500. It’s certainly not cheap. You can find some high quality 6.7 Cummins turbo upgrades for around the same price as OEM, if not even cheaper.

Turbo upgrades are a good route to go – in our opinion. It will allow you to extract a little more performance from your Dodge or Ram truck. However, turbo upgrades are still a good option even if you want OEM performance. A larger, more efficient turbo will have an easier job and should in theory hold up longer than the OEM turbo.

3) Heater Grid Bolt Causing Engine Failure

The heater grid on the 6.7 Cummins has a bolt on the bottom side of it that holds a metal conductor in place. Heat causes this bolt to melt which can then cause it to either break off or loosen the stud and completely fall out. When this happens it gets sucked into the intake manifold and then into the cylinders causing complete engine failure.

This issue is becoming more common as these engines get older – so far it has only happened on 2007.5-2018 models. The failure rate isn’t known but this can easily lead to $20k+ of repairs so the problem is very serious.

We’ve written a full guide on heater grid bolt failure and upgrades you can make to prevent the issue in a separate article. It’s worth a look and highly recommended to address this issue immediately to prevent it from happening as it can happen at any time and cause almost immediate failure.

4) Head Gasket Problems

Head gasket problems on the 6.7 Cummins may not be too common in actuality. However, compared to the previous 5.9 Cummins engines the B6.7 runs into the issue a lot more frequently. Part of it may have to do with the sheer power and torque the Dodge Ram 6.7 makes. High cylinder pressures may be to blame for the head gasket failures.

Chances are head gasket failures are somewhat blown out of proportion. In other words, it’s likely not as common as some may suggest. It’s still worth the mention though since head gasket replacement can be pretty pricey. When the head fails some opt to upgrade the fire-rings and head studs to help keep the head from lifting.

Head Gasket Failure Symptoms

  • White’ish smoke with sweet smell
  • Oil mixed with coolant
  • Coolant mixed with oil
  • Overheating

A blown head gasket will likely allow coolant into the combustion chambers. This will result in white smoke from the exhaust with a sweet smell from the coolant burning. Additionally, blown 6.7 Cummins head gaskets can allow oil and coolant to mix together. Higher pressure in the cooling system can also result in rapid overheating and/or coolant pouring out of the tank.

Replacement Options

Replacement costs can vary depending upon the year and model of the Dodge or Ram truck in question. Fortunately, there is only one head gasket thanks to the straight-six design. 6.7 head gaskets run in the ballpark of $100-200. Labor is where the costs begin to add up, and the repair can come in excess of $1,000 all in. That’s also assuming you’re not upgrading any parts.

Some 6.7 Cummins owners look to kits like this ARP head stud kit to avoid any potential issues in the future. The kits are expensive, especially when you add in labor. If you’re looking for a less expensive alternative, we recommend at least upgrading to the ARP head studs.

5) Fuel Dilution Issues

Alright – we’ll speed things up a bit moving through these next sections. Some fuel dilution in the oil is natural on the 6.7 Cummins engine. It’s inherent due to the way the engine manages regeneration. This is the process in that particulates are trapped in the DPF and burned for cleaner emissions. The 6.7 Cummins does not use a 7th injector to introduce fuel into the exhaust. Rather, the fuel injectors spray some fuel into the exhaust stream during the cylinders exhaust strokes.

This allows small amounts of fuel to stick to the cylinder wall where fuel can then mix with the oil. Some fuel dilution occurs in almost all diesel engines. However, some 6.7 Cummins diesels seem to have too much dilution. Dodge and Ram state the acceptable limit at 5% dilution.

Anything higher can be an issue since too much fuel can interfere with oils job to properly lubricate and protect the engine. It won’t cause any immediate and severe damage on the ISB 6.7L engine. However, it can result in premature wear for engine internals.


There aren’t usually any immediate symptoms of fuel dilution on the 6.7 Cummins. As such, it’s a good idea to do an occasional oil analysis. This will help you determine the rate of fuel dilution in your specific B6.7 diesel. You can then come up with an oil change schedule based on that information.

How to Avoid Fuel Dilution

A few ways to help prevent too much fuel dilution on the B6.7 Cummins include:

  • Allow engine to warm up
  • Avoid extended idling

Allow the engine to warm up before driving under heavy engine loads, such as towing heavy weights. The fuel is less likely to stick to the cylinder walls on a warmer engine. Additionally, avoid idling the engine for extended periods of time. This somewhat ties into point one. If the Cummins 6.7L diesel is left to idle too long the cylinder temperatures drop. This will increase the amount of fuel sticking to cylinder walls.

6) EGR Cooler Failure

EGR issues are a problem among many modern diesel trucks. The B6.7 Cummins is no exception here. It’s true most modern diesels primarily have issues with a lot of the emissions related equipment. As such, long-term diesel owners are likely well aware of these problems. We’ll keep this pretty short.

The EGR valve and cooler on the 6.7 Cummins is known to have problems, especially with higher mileage. It’s common for owners to simply delete the EGR system when problems do pop up. Of course, EGR delete can have legal concerns due to emissions laws.

Sometimes cleaning the EGR valve will help alleviate issues. Though, it’s usually a good idea to replace or delete the parts – especially if your Dodge or Ram 6.7 is higher mileage.

Dodge Ram 6.7 Cummins Reliability

Is the Dodge and Ram 6.7 Cummins engine reliable? Yes and no. The 6.7 diesel certainly doesn’t have the same reputation as some of the older diesels like the 5.9 Cummins or 7.3 Powerstroke. However, many modern diesel engines are in the same boat as the 6.7 Cummins. A lot of the emissions related technology can really kill these diesels. DPF and EGR problems are a few of the emissions parts that can cause headaches on the 6.7 Cummins engine.

That said, the 6.7 Cummins is a fairly reliable engine overall. This is especially true if you opt to delete some of the emissions equipment like the DPF and EGR systems. Beware of potential emissions or legal implications, though.

Otherwise, maintain your B6.7 Cummins well and it will likely reward you with a solid, reliable experience. It’s a good idea to perform the occasional oil analysis to confirm fuel dilution. Work out an oil change schedule based on the results. Keep up with other basic maintenance and stay on top of repairs as 6.7 Cummins failures occur.

Again, the 6.7 Cummins may not have the same legendary reputation as some of the older diesel engines. When well maintained the ISB 6.7L should still hold up well beyond 250,000 miles. We’ll consider that pretty respectable longevity.


The Dodge, Ram ISB 6.7L Cummins is an impressive diesel engine. It was the first light duty truck to break into the 1,000 torque territory with the 6.7 Powerstroke following shortly after. There’s no question the 6.7 diesel provides plenty of power and torque for almost any owner. However, no engine is perfect and this applies to the Cummins 6.7.

It’s mostly emissions equipment that brings the engine down a little bit. EGR and DPF problems are common on the 6.7 Cummins – as well as many other modern diesels. The sheer torque of the 6.7L engine can also cause issues with the head gaskets failing. Otherwise, turbo problems are possible with higher mileage as they take a lot of abuse. Fuel dilution is also another area that can be an issue, but the occasional oil analysis will help mitigate the risks of dilution of the oil.

Dodge and Ram trucks with the 6.7 Cummins engine are pretty reliable, overall. Sure, it doesn’t have the same legendary reputation as older diesels like the 7.3 PS or 5.9 Cummins. Unfortunately, the emissions parts of the modern day work against reliability in many ways. Nonetheless, maintain the 6.7 Cummins well and it shouldn’t have any issues eclipsing 250,000 miles.

What’s your experience with the 6.7L Cummins straight-six?

Drop a comment & let us know!

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  1. I have a 2014 dodge ram with a 67 Cummins diesel and I would like to know why did the catalytic converter go out in my truck at 80,000 miles

  2. I bought a 2007 RAM 3500 with the 6.7L at 325,000 miles for 18K with a great body, interior AND brand new warranted 68RFE Transmission. In the last 5 months I have put over 9,000 miles on it and it is running amazingly well. My 6.7L now has 334,000 miles and I later found out that it has all of the EGR and DEF deletes done to it.

    After every 3,000 mile oil change the oil has a nice amber color to it and not black like my old 7.3 idi. It has a level 1 Juice 2 Edge tune built into it I believe since the interface is missing but the cable is still there and it is a nearly smokeless Diesel. This is really strange to me and I’ve never seen anything like it.

    It has great power, the oil is always clean and it pulls amazingly well. While unloaded and in 6th gear I drove it for 35 miles on level ground between 55-60mph and it averaged 26 MPG!!!

    I have never heard of a 3500 truck being able to do this let alone a high mileage engine at that. I recently pulled my 28 foot 4 place snowmobile trailer with a heavy turbo Yamaha Viper 4-stroke and a Skidoo 850 plus a generator, gear and my buddy over Snoqualmie pass. The truck went no slower than 65mph and never needed to go any lower than 4th gear.

    As far as I know the only thing done to this 2007 6.7L are the Deletes and a level 1 tune. Probably in the neighborhood of 375Hp and about 760 ft/lb of torque. I was never a Dodge fan until I purchased this truck 5 months ago. I am very impressed with it.

    The guys at the Valvoline Oil Change facility in Marysville, Washington told me that they have NEVER seen a diesel truck with engine oil as clean as mine. I give this 3500 Laramie package a 5 star plus rating. Loving my new RAM and I am a HUGE fan of the 6.7L! 🙂

  3. 2013 RAM 6.7 L Diesel, 100K miles: While on vacation and towing a travel trailer from Gunnison,CO with my two young daughters in the truck, home to the Loveland,CO area, the truck suddenly lost power while doing about 55 mph, forcing me off the road and onto the shoulder. About a minute after the truck went into limp mode, I got a “perform service” message across my dash. As I pulled off, the power steering went out making it incredibly difficult to steer my truck/trailer onto the shoulder. Then the engine died and would not restart. Once into a shop in Gunnison, they replaced the starter (which had not been having any discernable issues), and then called and told me I need a new engine. What? This truck has performed almost flawlessly since I bought it used in 2016. The truck is now being towed to it’s “home shop,” a dodge dealership in Longmont, CO. Based on what I read here and on other sites, I suspect DPF clogging started this cascade of events, However, the truck was running normally the week prior, no signs of impending engine failure that I knew of. Now, I need a new engine? I just paid this thing off and was expecting, at least, another 100K miles plus. I can’t afford a new engine….I’m just praying the dodge dealership finds that not to be the case and the solution is more simple/less expensive. In any case. It put the safety of my children at risk with this spontaneous loss of power, steering control and engine failure while pulling a travel trailer. I survived a rollover while towing a trailer some years ago, so I am very safety cautious. Just based on how this truck shut down so suddenly, creating a safety issue for my family, I will never buy another 2500 again. Should the truck need a new engine, I don’t know what I’ll do. Thoughts?

    1. Here’s the thing: when an engine shuts down you will lose power steering assistance. This is true on any full size, one ton truck! This is not the fault of any particular manufacturer. The power steering is simply powered by the engine. If an engine has catastrophic failure, and stops turning this is what occurs. That said, it sounds like that first shop didn’t have any business working on a diesel. I’m guessing they cranked the engine until the starter burnt up, then charged you for the new starter.

  4. Ok I have a 2012 ram 2500 has the 6.7 Cummins
    Yesterday I was in a rush I drove to my mother-in-law’s house and I had an emergency call as soon as I got there well I back up fast and I hit the rev limiter a few times then put it in drive and it felt like no power it didn’t have any boost well I get to where I’m going and start looking at it and turn it off then I turn the key on my boost gage said it had 5.9 not even running and I have a edge programmer I even had a buddy bring his snap on scanner and look my blades is fine not loose I just don’t have boost and don’t know what to do I’ve checked all the hoses any help would b appreciated

    1. Try a bypass relay for the vgt has something to do do with map/maf signal
      Had to replace my fuse box due to cold solder issue

  5. My Son and I both bought new Rams 6.7 diesels (2021) . The both have over 2500 miles and both started to have this howling/high air flow sound from under the hood when starting out from stop but stays making that sound through the first couple gears and then goes away until the next stop sign where it does it all over again. Outdoor temperatures are 60-95 above f. It doesn’t always happen but most of the time it does. Not when driving above 40 mph.

  6. I have a 2013 Ram 6.7l. On deceleration I hear an intermittent low sound of a growling only when deceleration. This does not always happens.
    I’ve heard of others with the same symptoms described but have not heard of any solutions to fix the problems.
    Is this something that you can help me with or can you direct me to somewhere else for help?
    Appreciate your assistance on this problem.

  7. I have a 2012 2500 Ram 6.7 I deleted the egg and added a 4 inch as exhaust with muffler, everything OK for a year, now when I push for power it hiccups and spews black smoke out, if I let off the pedal and go gradually up to speed I’m okay, what needs to be cleaned?

  8. I have a Dodge Ram 2500, 2009 6.7 liter engine, and I’ve had enough, problem after problem, steering, exhaust. I think I have solved the problems and always something else. For Sale – 112,000. Dodge should be ashamed.

  9. I have a dodge 6.7l turbo diesel. There are 234oook on this engine. I recently did a north americian tour and put 30,oo0k on it. Today as I crested a fairly high hill in Eastern Quebec and the engine just stopped pulling. It kept running without of r p m but would not pull the truck and trailer. I’m currently sitting in my toyhauler wondering what is wrong. Now it won’t start and the fan and belts don’t turn when we try to turn it over…. any thoughts. …please help.

  10. I have a 3500 one ton dodge ram truck with 6.7 cummins engine. I have 35,000 miles on this
    truck and my engine has failed. what would have caused this problem with an engine with
    this few miles??

    1. Hey Eddie – did the dealer or a repair shop give you more details on what specifically failed? There are a lot of things that could cause this so a bit more info is needed on what happened to try to determine the cause.

  11. 2012 3500 Ram with 71 thousand miles on it. Never have used Def, no place to put it in, when it’s cold outside I let it idle, bought it new in 2012, Drive it to Fairbanks alaska once a month 250 miles round trip .I use Rotella full synthetic, got hard to find, Might need to switch oils. Great truck

  12. Bought my 2015 ram 4500 brand new. The article above was spot on. After about 100,000 miles I started having DPF problems., then turbo failure. Just found out today that the engine has to be replaced due to a Valve failing and destroying the piston. It appears that this all started from the DPF being 100% full and trying to drive it during the regen process.
    I am not a dodge ram and Cummings fan now.😟

  13. Have a 2012 3500 ram mega with 6.7 , have 208,000 miles I think I need to replace turbo an delete the junk. I was on my way to California an my truck engine went into limp mode an I got a message my cat was full an would not regin, a old mechanic told me to get 3 bottles of sea foam an dumb into diesel an don’t look back but keep my foot in it, smoked like hell but I got to California

  14. I have a 2010 dodge Cummins 6.7. I replaced two 02 sensors last year and now the engine light comes on again. Computer check says the sensors are faulty. Is there an underlying problem causing the sensors to fault or something else is wrong?

    1. Hi Craig,

      There are a number of possible underlying issues that can cause O2 sensor failures. One major one for 2010-2012 6.7 Cummins engines is the O2 sensor overlay harness. There is actually a service bulletin for this issue, which you can find by searching for TSB 25-002-14. Hopefully that solves the issue for you.


  15. I have a 2020 3500 with 15,000 miles and have had an ongoing issue with code PO299….turbo underboost. As it’s still under warranty it’s going back to the dealership for the 5th time but they haven’t been able to solve this issue yet and I suspect they won’t this time around either. So……any advice? They’ve already replaced the air filter (which to me seemed ridiculous as I used aftermarket filters for 2 yrs without an issue) and replaced a supposedly cracked EGR cooler, but the issue has persisted. The code implies that it’s the turbo which I suppose is possible, but I’m more inclined to believe it’s something on the intake side dealing with EGR or the exhaust and DPF system?? Any help would be greatly appreciated!

    1. Hi Tony,

      Have they checked the TMAP sensor? The sensor reads boost pressure so if it isn’t working properly then it can’t send the right data back to the PCM and may lead it to believe boost is under target. Otherwise, checking for boost leaks is a good idea. If it isn’t the sensor or a boost leak then it could be a lot of other things including EGR issues, an actual fault or failure of the turbocharger, etc.

      Ultimately, if the dealer can’t figure it out I’d recommend trying another dealership. As a last resort you could maybe try an indy shop and then work with corporate to comp the bill. They should do that if the dealer couldn’t fix the issue in 5+ attempts but that could turn into quite the hassle and headache. Best of luck getting your Ram 3500 issues sorted out.


  16. I have a 2009 Ram 2500 with 6.7L diesel. Seems to run fine, but when I step on it, you can innitially hear the turbo spin up but then there is a snuffled- clatter sound and the boost is less then expected. Eventually the power comes on but, less than desired. What’s causing the sound?

  17. Have a 2022 ram 2500 with a 6.7l Cummins, bought it used at 42000 plus miles. Previous owner was enterprise rental so I know it was PM’ed rightfully. Been in to the dealership 3 times since I bought it in February, going in for the 4th time for a dpf full warning. Truck shut down on me the last time and left me stranded , what’s the issue with the filters?

  18. Have a 2008 6.7 Cummings, 4×4 mega cab automatic, run fine four 1 hour then power loss but keeps idling, I I floor gas pedal it usually starts running correctly again.also sometimes taking off no power then, until it floor it t

  19. I have a 2012 cummins 6.7 high output diesel , some times i get a little puff of blue smoke out the exhaust , it has 83,000 miles on it . what could cause that ?

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