Internal combustion engines are the fussiest things. Properly built and maintained, some will run for hundreds of thousands of miles, perhaps millions, while rarely if ever letting their owners down. And yet, sometimes all it takes is for one little fastener or clip to fail, and you’ll see whole engine trashed in mere seconds. The Cummins 6.7-liter diesel is an engine that can apparently suffer from that very affliction.
The Cummins 6.7-liter engine is the turbodiesel star of the Ram 2500 and 3500 lineup. It’s currently the most powerful engine option for those trucks, offering up to 400 horsepower and 1,000 pound-feet of “clean diesel torque” according to Cummins. The engine has been available in the Ram pickups since 2007. It’s prized for its good fuel economy and reliability, and Cummins even says it can go 15,000 miles between oil changes. But it’s got one wacky flaw, and while it’s rare, you really should be watching out for it.
So what’s causing this problem? It’s all down to the grid heater. I’ll explain!
A Loose Nut Gets Sucked Into The Engine
The “grid heater” is a resistive heating element that sits in the intake of the Cummins 6.7-liter engine. Its role is to heat the incoming air to make it easier for the air-fuel mixture to ignite in the cylinders. It’s essentially doing the same job as a glow plug. However, instead of being installed on a one-per-cylinder basis, the grid heater is able to warm the intake air heading to all cylinders.
The problem with the grid heater is actually quite simple. A metal stud passes through the body of the grid heater, carrying 12-volt power to the heating element, and is held in place with a nut. Unfortunately, under certain conditions, that stud can fail, or that nut can come loose. In that case, the metal object tends to fall through the intake and directly into one of the cylinders, usually cylinder #6. At this point, it will usually impact the valves, the piston, the head, and the cylinder walls in short order. It does a great deal of damage in the process, usually necessitating an engine rebuild.
But why does the stud and nut fail? This can happen for a number of reasons. For a start, the stud and nut can get very hot. They are right next to the heating element itself, and on top of this, they carry a great deal of electrical current. Furthermore, as the engine ages and the stud and nut get dirty or corroded, the electrical connection between them can become poorer, leading to more resistive heating of the connection. Between regular thermal cycles and engine vibration, it’s no surprise that this stud and nut come loose or occasionally even snap in the field. In extreme cases, if the solenoid controlling the grid heater fails, the heater can become stuck on, and the stud and nut can allegedly even melt off.
Diesel tuners Banks Power note that the problem was once thought to only affect Ram trucks in colder climates, where the grid heater was used to a higher degree. However, company notes it has since seen the problem in engines from across the country, including those from warmer climates.
Thankfully, the problem can be caught early. Banks Power notes that a damaged grid heater stud and nut will not conduct electricity as well as it should. The high resistance of the connection can trigger check engine codes—either P2609 (Intake Air Heater System Performance) or P0542 (Intake Air Heater A Circuit High). This is a surefire clue that the grid heater should be physically checked.
The grid heater can also be checked manually. Getting to the stud itself involves removing the intake elbow, fuel lines and intake plate. It’s not a huge job, but not a small one either. However, an easier test can be done without disassembly. There’s a 12-volt lead that hooks up to a connection on the top side of the grid heater, which is directly connected to the stud itself. Wiggling that connection can give you a clue as to the state of the stud. If it moves easily or is excessively loose, it’s a strong suggestion that the stud has already suffered significant damage and could be broken or close to breaking. Indeed, Banks Power notes that in several cases, a damaged stud can be sheared simply by hand action. In these cases, the grid heater should be fully removed for checks and repairs prior to starting the vehicle. Else, there is a high chance of the engine ingesting a dropped nut or broken stud.
Banks Power notes that no recall or service bulletin has ever been issued for the grid heater stud issue. Ram has recalled certain 2021-2023 model year trucks for issues with the relay that drives the grid hetaer, but not the grid heater itself, based on searches conducted by The Autopian.
So what is the fix? Well, if the grid heater stud is damaged, replacement is the obvious solution. However, given the original design is subject to failure, replacing with stock parts is not an ideal permanent fix.
Alternatively, you can look to the aftermarket. BD Diesel sells a number of kits that claim to solve the problem in different ways. You can delete the grid heater with a simple kit and intake mod, but you’ll lose the benefit it brings to cold starting performance. The company also notes that it can’t ship this to California, presumably for emissions reasons. It’ll also make your truck throw intake heater codes unless you get a tuner to code that out. Alternatively, you can buy an upgraded busbar kit. The thicker metal part has lower resistance to reduce heating, and it’s also designed with fasteners that can’t drop into the intake. You can see it installed in the video below.
I strongly doubted that the grid heater could draw 200 amps, but I’ve since found sources backing that up. No wonder these things are getting hot!
Banks Power has a fix too. At this point, it’s worth noting that the company made its video on the problem in part to sell its MonsterRam intake. The MonsterRam is installed in place of the stock air intake, and involves removing the stock grid heater. This obviously solves the problem of the stud failure by removing the assembly entirely. The custom intake instead features a coil heater to supply warm air for easier cold starts.
Prevalence?
The thing we don’t know is how often this problem occurs. Companies that make products to solve this problem want you to know about it. That’s helpful to a degree, but it doesn’t tell us whether this is an every-truck problem, or something that happens in incredibly rare cases.
The Autopian has contacted Ram for comment on this matter. The automaker may have the best knowledge of how often this happens in the field. One suspects, though, given no recall has been issued, that it may be quite a rare occurrence.
Research on the wild Internet can really only tell us it exists. Anecdotally, there are plenty of posters on Reddit saying that it’s a fairly rare issue. Similarly, parts shop Geno’s Garage says that the problem is “very rare,” while noting in a tech tip document that Ram (or perhaps Cummins) has machined a flat spot in the nut to try and avoid it backing off under vibration.
If this problem was happening regularly, and within a period of three to five years or so, it would be causing all kinds of headaches for warranty repairs. We’d also see complaints splattered all over the NHTSA website. Ultimately, it seems to be something that can happen, but not something that definitely will happen. In the words of the Australian government—be alert, but not alarmed.
In any case, you can use the wiggle test to verify for yourself if your engine is at risk or not. Between that, and paying close attention to your check engine light, you should be safe enough. But if you’re really, truly scared of the little bad bolt ruining your engine and your day, you at least know that there are solutions available. Happy diesel motoring!
Image credits: Banks Power via YouTube screenshot, BD Diesel, Ram, Geno’s Garage
As a well-known and confirmed “loose nut”, I can testify that I can ruin a diesel engine in moments.
didnt dodge also have the cotterpin of death on the old 5.9 cummins that would grenade the whole thing? they never learn.
Is it just one nut, or is it bofa?
Suddenly, squirrels everywhere have an idea…
I don’t think this should be a hot take, but I just don’t think there should be any form of fastener within any vehicles intake tract? Seems like it should be something pretty easily avoidable, yet here we are.
Excluding some vehicle throttle butterflies, I’ve only encountered one other car where the design of any part would allow for a nut or bolt to drop into the intake post-filter and that was an aftermarket airbox housing on a modified turbo MX-5.
Turbos commonly have a nut holding the compressor wheel on.
I’ve seen fasteners inside superchargers too, holding charge cooler bricks and manifolds, but always with a feature that stops the fastener undoing far enough to fall out, even if it were loose.
Fasteners in the clean side (post filter) of the intake system aren’t prohibited, but you do a lot to avoid them. You have to get a low occurrence on the DFMEA because the severity of failure is so high.
This Cummins nut should be retained by that deformed section of thread on the stud, so mechanically its probably fine, but that allows the secondary issue of electrical load heating it up once it’s loose. The fact that this gets flagged as a MIL light suggests that this failure mode was predicted and the mitigation is that light.
I wonder how many failures were preceded by that light being ignored?
Not going to lie, absolutely embarrassing to have forgotten about the turbo impeller nut, which I have seen one or two of take an impromptu trip down stream.
I appreciate your input (and that of the other comments) on different examples, I definitely haven’t seen it all, it’s just something that feels avoidable, but I’m in no position to claim that it entirely should be, and as you pointed out, it does have to pass a certain standard.
For this specific fastener, it seems like there are many cheap and easy solutions. Lock washer, cotter pin, etc.
I’ve worked in manufacturing my whole career so I’ve always felt this tug of war between the bean counters and product specs. And I get it. An optimized assembly line is *chef’s kiss*. But I guess the bean counters won this fight. “We saved 1 cent and 5 seconds of assembly work per unit!”
Ford recall 20E04 for their 3.0L diesel with a thrust washer that could break off and end up in the engine. I’m pretty sure there are plenty of other items that could end up in a combustion chamber. I know that glow plug tips have been known to break off and achieve the same end result.
Have a 2018 2500 diesel. This discussion is practically laughable in most forums. Don’t get me wrong, it can happen. But unless you are Banks and trying to sell a “solution”, there’s a better chance ify my truck being disabled by lightning than the bolt.
In general, Banks is a bunch of snake oil, at least in the Cummins world. Like cold air intakes, as another example. The stock air box can handle 600hp and installing a CAI on a stock motor basically does nothing but make your wallet lighter. Right up there with K&N filters.
Anyway, any Cummins owner with basic knowledge knows about the jiggle test, etc. I think the article got caught up in the Banks hype rather than real world numbers.
Fair assessment. I think like, a lot of owners know, but this was news to a lot of us and I think worthy of covering.
I can’t attest to anything diesel as I never owned one, but the K&N filters I can speak on. I have used them in basically all of my vehicles over the years. Everything from NA Miatas to my 2008 Tacoma to my 2024 Mazda3. While I doubt their claims of adding horsepower do anything based on seat of the pants testing, it has changed power delivery on all of my cars and I have seen slight increases in MPG.
I have only ever done drop in filters and on my Miata, I saw quicker revving from 2-4k and about the same on my truck. On my 3, I saw a pretty good bump in MPG from pretty steady 270-290 miles per tank to 300-320.
I agree on your estimation of K&N filters. I’ve used them on a number of cars over the years. No filter can overcome the performance limitations of a restrictive air intake. But on cars with fairly high intake airflow rates and relatively small air filters, paper filters’ flow degradation as they fill up with particles tends to be more noticeable in terms of “softer” power delivery on throttle transitions and a small but steady decrease in fuel economy.
K&N and other cleanable/reusable types of seem to do a better job of capturing particles more evenly across the filter medium, not just piling it up in the creases. The total surface area of the filter medium tends to be utilized more evenly over the course of time between cleanings, which can make a small difference.
It’s probably really more of a packaging problem in the design of the air filter in these cases. Larger filters would have more area and be less susceptible to having their useful area filled up with particles sooner. But in cramped engine bays, a larger filter may not be possible. So, a smaller filter with better performance characteristics over time as it gets dirty is the next best alternative.
I also agree K&N you can actually find videos online of different filters from them and sure they might not be the best at filtering but that is the point they are for performance applications where you are looking for better flow. I think Project Farm on YouTube has done a video of their oil filters and possibly their air filters at one point.
I’ve seen back to back engine dyno (not vehicle dyno) testing of various aftermarket filters vs OEM with proper a-b-a tests on a shiny new engine. No improvements over OEM on that system (nothing repeatable that was bigger than the test error anyway), although I designed the system and I might just be awesome.
We spend a lot of time ensuring the flow through the filter uses as much filter area as possible to reduce pressure drop, and that also spreads the dirt around evenly. Dozens of CFD iterations, lots of time validating the analysis with testing.
Most aftermarket filters are fitted replacing dirty OEM filters, so performance gains are expected.
That’s a pretty awesome job to have right there. I wouldn’t expect there to be any real performance gain from an aftermarket filter to a new one as people like you design them to be pretty optimized I would imagine. Especially if you’re testing those on a brand new engine.
I can say the filter that I took out of my Mazda3 had 15k on it and even when brand new and past the break in period, I didn’t see the MPG as good as when I put the K&N in it. Take that for what it is from some unexperienced guy who drives a lot ha
I agree that the overall system is the biggest limiting factor. With the K&N being thinner, of course you’re going to get better air flow because there is less material to have to suck air through, which also would lead to better distribution of contaminants that it picks up.
Maybe? I mean are you going to feel a 1-2% increase in power? Realistically, can you logically expect anything than maybe a few HP more under the best conditions just by switching out your air filter? Unless the OEM was a complete engineering failure, there can only be a tiny increase in power that it’s most likely just a placebo effect. Practically every test that is not sponsored by K&N shows this. Right up there with how Slick 50 will lower your RPMs due to its teflon technology in the oil!! I can remember people using stuff like that and telling me they are running at lower RPM at 65mph and their idle speed is now lower. Uh, adding teflon to your oil does not change your gear ratio, LOL.
Ha! Haven’t heard about the Slick 50 before. I don’t drink the KookAid too hard when it comes to K&N specifically, but I have had enough experience with them over the years with a wide variety of cars that I keep coming back to them. If somebody were to ask me, what have you done to that ride man? I’m not sitting there saying “dude, I’m rocking that sweet K&N drop in filter! It lowered my 0-60 by .001 seconds!”
I use exclusively K&N filters just because it’s cheaper if you keep the car for a long time. I buy one $50-80 filter, and never replace it. The cleaning kit is cheaper than a paper filter, and lasts for 5-6 cleanings, so by about 60k miles, I have paid off the K&N and everything after that it’s saving me money. I have never noticed any performance benefit, or MPG, but in the end it is cheaper. So I go for it anyway.
Good article, wish more attention was brought to bad design like this more often. Id take glow plugs personally. Much less often for them to break into the engine and on my tdi they are easy to change.
My wife is not a car person got a good laugh about “GRID HEATER NUT JIGGLE TEST”
Any chance your wife is either Beavis or Butthead?!
I ran a series of tests and can conclusively say that she is not.
“Fire”
Why do I feel like this could also be solved with a single tack weld…
Lock washer? Loctite?
It looks like it’s the entire stud failing in some cases (see the pictures somewhere around the middle of the article), so even securing the nut might not help.
(This pipc https://images-stag.jazelc.com/uploads/theautopian-m2en/RAM-6.7L-Grid-Heater-Bolt-Failure-Explained-00-01-20.jpg)
The studs have deformed threads to stop a nut from falling off if it gets loose. You’re correct.
You know why the studs fail? They get hot when the damn relays get stuck on!
You would think Cummins learned from the 5.9 dowel pin of death but I guess this either missed in testing or dismissed as an edge case.
That’s a lot of stress on one bolt. I can understand it happening.
Geno’s Garage/TDR Register is a great source for Cummins issues. If they say the problem is very rare, I would tend to believe them. The “Killer Dowel Pin” seems to have been a bigger problem on the old 12-Valve 5.9 Cummins ( I had a 1996 1-ton pickup,) Maybe that’s why it was nicknamed the “Killer Dowel Pin.” Aftermarket “fix kits” were available and solved the problem.
Yup, TDR is easily the best source for all things Cummins.
First thing that came to mind when I saw the headline.
Same here but funny thing is my 1st gen Cummins had over 200k on it when I bought it and the KDP had never been done (I have bought a cheap kit and fixed it) so no idea how much of an issue the KDP really was.
There are so many of those 1G Cummins out there (more than just in Dodge pickups) that it probably comes up from time to time, and the catastrophic damage that happens when that pin finds its way between the gears is pretty spectacular.
Haha I am sure it is. I have seen forum post where someone has gone to do a KDP fix and the pin is just sitting at the bottom after opening the cover. Those engines must have been blessed by every matter of priest, rabbi, cardinal and so on when they were built haha
You had this whooooole article to set up a “the nut behind the wheel” joke but no, you had to share useful information and good insights into the failure rate, failure mode, and motivations for fixers trying to sell you stuff in a clear and straightforward manner.
For shame.
I mean, that loose nut could do an equally good job killing the truck whether it had the Cummins or 6.4 Hemi.
I was gonna say, that’s the part that causes the most damage to these.