Three 5th Gen Cummins Engines... SAME Exact Failure Every Time!

Added: 2026-05-22

[00:00:00]We have a unique opportunity here. I've got three fifth generation 67 Cummins. Me and Jake are going to tear these down. He's already tore one down. Tell me about this motor, Jake.

[00:00:11]You tore this down.

[00:00:12]>> Yes, it did.

[00:00:12]>> Um, what did we find on it?

[00:00:14]>> Uh, the first two pistons uh were beginning to melt.

[00:00:19]>> Where they at?

[00:00:20]>> Whoa. This baby got hot.

[00:00:22]>> Oh, yeah.

[00:00:22]>> Let me see another piston just for just >> Yeah, right here.

[00:00:28]So, you're like, you're wondering, how did that happen? You know, how did all that metal disappear? Well, it melted. It literally spray welded itself, so to speak, right off the piston. It when it when it melted, well, it actually didn't seize that ring up, which is amazing. Got dang close to it.

[00:00:49]You can see it took off the aluminum here. And this is a steel. This is actually a good thing to see here. So, this top ring actually has a steel insert that's that's molded into the piston.

[00:01:03]And we we we've actually burned the aluminum alloy away from that right down to the steel insert and did the same thing on this piston. What causes that?

[00:01:13]Heat. Okay, let's go a step further.

[00:01:16]What's causing the heat? You got to have an oxidizer, which is the oxidine. You have to have a fuel source. Diesel. When you get too much of that, there's plenty of air in a diesel engine. And I say that because come here. Let me show you something. A diesel engine is a little different. That's the intake on a diesel engine. I mean, that's how much air we're trying to get inside this engine to make it run. A carbureted engine that was a 6.7 L, which would be a big block.

[00:01:44]That's a pretty good size engine. You could have a throttle opening about that big. It could it could be a third of that size. So, you always have plenty of air in a diesel. And when a fuel system goes rogue, meaning the injector, hangs open, doesn't spray, right? Um, you got excessive fuel. A diesel does not rev up by adding more air to it. That's how a gasoline engine works. You'll add more air to the engine. You have a throttle plate and, you know, broom, it revs up.

[00:02:11]On a diesel, you add more fuel. And if you add too much fuel or something like that, you can have a runaway on a diesel. It's kind of an uncommon problem now. It used to not be when it was mechanical injected, but uh anyway, that's why those pistons are melted.

[00:02:26]This engine went down for a fuel system related issue. Sometimes the lifters will start eating up the cam on this and we've seen that and I've talked about why that happens.

[00:02:39]So, we'll go through that again and I'll show you on this one with a roller lifter.

[00:02:45]Just lay that up across the thing right here. Thanks, JJ. Everybody say hi to JJ. He's a new guy around here. We love him. We love him. And uh JJ, how long did you try to get a job here?

[00:02:56]>> Five years.

[00:02:57]>> Five years. Persistence wins. Okay.

[00:03:00]That's how you win in this world.

[00:03:02]Persistence. You're a winner, dude.

[00:03:04]>> Okay. So, the lifter rides on the lobe like this.

[00:03:09]And what we're finding is a lot of times this cam is not doesn't have the chatter on it. We we're probably going to find one on one of these motors we're going to tear down. But the lifter starts doing this in its bore. And it when it does that, it causes fretting on the roller and on the cam lobe here. And and we'll show you what that fretting looks like probably when we tear this down.

[00:03:31]But why does that happen? Well, a roller lifter is not like a flat tapet lifter.

[00:03:36]A flat tapet lifter kind of looks something like that. and it rides on here and it's designed to turn and rotate because or you'd have a flat area on here. That's not a lifter, but that's what kind of one would look like a flat tapet. A roller has to stay straight. It can't start rocking back and forth like that. These lifters are rocking back and forth like that. And we got to fix. So, let's let me show you why they're doing that. inside this motor. They've taken this little this area right here and they've taken an endmill and they've just dropped down in it. Well, look what look how much play we got in it. I'm going to put the lifter in there. So, that lifter, you know, when it's going up and down on the cam is is going back and forth like that. And that back and forth vibration is causing fredding. So, it's wearing out cam loes and ruining lifters. That's that's this is the weak point in this fifth generation Cummins.

[00:04:29]This generation Cummins started in 2019.

[00:04:32]So if you got a 2019 Cumins, you got this issue. The other problem is the rockers. Let's look at these rockers. Oh my gosh, these things are poster child for nasty. Look at that cup. Look at that. So the push rod goes in here. It's upside down. This is actually the way it goes. But this shouldn't fall off of that ball. That that should not happen.

[00:04:53]Look how it's all degrading. That's a piece of metal. That thing's worn itself right down. There's not enough lubrication in that. And why is there not enough lubrication in that? Here's the problem. All right. So, this is first generation all the way to fourth generation. This is how the rocker arm assembly worked. Now, hold up this this rocker next to me. Turn it over. And so, this is fourth generation. So, this went down onto the lifter. This came up and was on the valve train and it sat in there like this. Okay. Now, what do you see different here? You see the push rod is is flipped over on this push rod. What do I have? I have a little reservoir there for dry startup. So when I start it, I don't have this area always has oil in it.

[00:05:41]Well, this design here, the oil just drains out of it. So your truck sits all overnight and everything, all the oil drains out of that little point that's metal to metal and you dry start it.

[00:05:51]That's what the problem is. That's why these are ruined. And the and the ends of these push rods look like Yeah, they look like that. Hold the hold hold the good one up here. See that end?

[00:06:03]How that's all threaded and the metal's all just wore off on there. So, there's the first thing. Now, you'll also notice what's the difference here is I've got an adjustment nut here. This style, first generation to fourth generation, this style here has an adjustable valve train. I think uh Cumins recommends you adjust the valves every 120,000 miles. I do it every 100, but uh that's what Cumins says. So, you have to pull the valve cover off and you have to do a physical adjustment here. Not a big deal. The roll the hydraulic roller lifter that we're talking about that's, you know, fretting and having a problem.

[00:06:41]You eliminated that maintenance item.

[00:06:44]Okay. But by eliminating that maintenance item, they've changed the design and it doesn't prove to be working very well. So this is the number one problem in the 67 comments. I I tear down these. This is the one that you can't avoid. You cannot avoid it. Okay?

[00:07:03]I mean, you know, your fuel system going down, the pistons I just showed you, you could avoid that if you had had a a pyro on your exhaust system. you'd have seen your exhaust temperatures going up and you'd know you got an injector that's going rogue on you. That's the best insurance you can have for melting pistons. Okay, a pyometer in as close to the exhaust as possible so that you're measuring uh accurate exhaust temperatures. I got a feeling Zach Hamilton will confer on this. We're probably the largest supplier of Hamilton cams in the United States.

[00:07:33]There's a link in the description and it'll take you right to our store to buy them. But let me show you what comes.

[00:07:38]You get a box like this. We've got I'll bet we got probably 30 of them in stock, but it comes complete. So, the cam is in a tube here, all safe, brand new cam.

[00:07:49]It's got our chrome molly push rods and and they've got the bucket back on them on the side that you want to have the oil retention. They're heavy duty thick wall. And here's our lifters.

[00:08:02]And they've been coated. So, we went back to a flat tap it with steel push rod.

[00:08:10]with our oil retention bucket at the top. So, we don't have the fretting like we've got that I've shown you. This has been in the Cumins motor for decades, and it works great. It even comes with some instructions, but if you'll see the first word here, pull cab. So, this isn't really a do-it-yourselfer, unless you want to pull your cab up off your truck in your in your garage.

[00:08:34]And it comes with a full set of rockers and they're adjustable. So, you'd be set to go. Now, listen. This is the only thing you can do on this motor to save this motor because of the design of that fifth generation with the roller rockers. Just put a flat tap cam in it.

[00:08:52]If you don't have any other issues on your truck, like let you know the truck is running great, you got 50,000 miles on it and you want to upgrade this, you can either order a kit from us or you can call us. We'll ship the truck here.

[00:09:05]We're getting trucks shipped here. It's not that expensive to ship a truck all the way from the east coast to us. And then you can fly out. Be happy to show you around the shop if you want or you can see Utah. It's a great, beautiful state and you can drive it back. Uh, but we can do the install for you here.

[00:09:20]We've done plenty of videos on on how to do that. What we're going to do now is we're going to tear down these other two motors. We're going to find out where they they went down and uh we'll discuss that further. So, let's get tearing down.

[00:09:55]Huh?

[00:09:57]Look at these rockers. They're a little different.

[00:10:00]Or I'm sorry, the rocket the uh the pads are different. These look like they've been machined. And on the other motors, they look like they're cast. They're a little different.

[00:10:11]These are smaller. I've never seen them like this. I wonder where this head came from. Is this a Brazil or Mexico head?

[00:10:17]Let's pull it off. We'll see.

[00:10:18]>> Yeah.

[00:10:22]>> Right away here, there's more of that.

[00:10:24]>> There you go.

[00:10:25]>> Oiling failure.

[00:10:26]>> See, look here. You have a you have a nice shiny push top of your push rod.

[00:10:31]Ow.

[00:10:33]Oh, it's okay. You can see the little burr right there on the top.

[00:10:38]Little pokey. Just gave myself a blood test.

[00:10:43]Yeah. Look at this one. Same thing. Look how bad that one is. It's just not the metal that's coming off of that. I mean, where's the metal going? It's going down into your engine. Those fine metal particles are being recirculated in the oil. So, it's not a good thing.

[00:11:01]So, basically, the rock arms, push rods, cams, lifters on all these fifth generations, they go in the trash can.

[00:11:09]They're They're basically junk.

[00:11:12]So, this head is made in >> Brazil. Brazil.

[00:11:17]Okay, >> let's go see what this head's from.

[00:11:21]>> Also Brazil, >> huh?

[00:11:24]Well, maybe they maybe just a year change.

[00:11:28]This one, man. Look at the sludge in this. It's not too hard to determine why that motor went down.

[00:11:34]Holy moly.

[00:11:36]And what what I got? I got bolt. I guess when they took the valve cover, they dropped some bolts in there. But I mean, look here. Look at this guys. This is not what you want to see in your engine. And that that's not good stuff.

[00:12:09]Boy, that sure makes that nice, don't it?

[00:12:11]>> Yes, it does.

[00:12:18]>> Well, first thing you see on this motor is there's no melted pistons. This one's got a little bit of degradation here.

[00:12:25]Little pitting on the side. You can see that.

[00:12:32]Oh, that one's got it, too.

[00:12:35]Maybe that's just a little carbon.

[00:12:41]Turn that head over. Let's just turn that head over real quick and look at the valve.

[00:12:53]All right. There's not a lot you can see. I mean, I don't see any, you know, cracking or any major burnt valves or anything like that. The recession on the valves is all the same. So, it tells me I probably don't have a burned up seat or anything. What I mean by recession is how far the valve is below the deck of the cylinder head here. There's actually a measurement for that on diesel. That's uh is pretty critical because you don't have a lot of leeway for compression ratio.

[00:13:19]But, um, of course, you know, the head will be disassembled and inspected and rebuilt.

[00:13:28]How do you want to do this? You just want to roll it over.

[00:13:30]>> Yeah, we'll pick it up and I'll pry bar on one side and we'll >> Okay.

[00:13:34]>> get it back down.

[00:13:57]I'll bet we're not going to find much wrong with this motor. I don't see any metal filings. I bet uh this motor probably we're going to find a cam that's bad was making noise and the guy replaced the engine.

[00:14:09]>> So, >> yeah, we don't really run into any bottom end issues on these. Not unless they were not maintained, >> right?

[00:14:15]>> The bearings are always good. You know, you you take care of this motor, it'll take care of you.

[00:14:28]Looks pretty good compared to that first one.

[00:14:58]Hey, heat.

[00:15:25]Heat. Heat.

[00:15:29]Heat. Heat.

[00:16:06]So, uh, the second motor we tore down, we found all that valve train issue. Was there any threading on the lifters or the cam?

[00:16:12]>> No, sir. I have a cam right here. I looked at everything.

[00:16:16]>> Um, >> so the loes look good. Gloves look good, >> but but the push rods and rock arms were trashed.

[00:16:22]>> Pistons, cylinder walls, all that look good.

[00:16:24]>> Yeah.

[00:16:24]>> Motor just uh needed needed the uh upgrade, I think. So, >> no melted pistons.

[00:16:30]>> Nothing. Look like it's had good oil changes and all that. Oh, yeah. The bearings look great. Mains look good.

[00:16:36]>> Yeah, I didn't see anything there.

[00:16:39]>> Okay. Yeah.

[00:16:41]>> All right. Now guys, that motor uh didn't have any sludge in it, you know.

[00:16:47]It just uh the fifth generation camshaft issue, >> just a time bomb.

[00:16:52]>> And I keep calling it camshaft issue. We should just call it uh valve train issues. Yeah, >> cuz it's really from the cam shaft up.

[00:16:59]>> All right, let's turn down number three.

[00:17:01]Tear down number three. And uh now look, this one obviously has been uh ridden hard and put up wet.

[00:17:11]I mean, this thing is just not good.

[00:17:13]Yeah, dude. I mean, it's this is so nasty.

[00:17:16]>> So, I'm not even going to touch this thing, dude. I'm >> I'm just I don't blame you.

[00:17:21]>> Yeah. Let's let you rip it down >> and uh let's let's start looking at it.

[00:17:26]>> Yes, sir.

[00:17:39]And there's one.

[00:17:42]>> So yeah, this one is more of the same, which is to be expected.

[00:17:49]>> Yeah, right there.

[00:17:58]Yep. There's another one right there.

[00:18:18]Way sludgy.

[00:18:21]It's everywhere.

[00:18:25]Have to change my gloves.

[00:19:00]Oh yeah, piston to valve contact right there.

[00:19:05]Yep. And right there. And right there.

[00:19:12]>> That one too up there.

[00:19:22]Yeah. Number three back.

[00:19:25]You can see it.

[00:20:02]I like it. Uhoh.

[00:20:06]Yay.

[00:20:12]>> How'd the head look, dude?

[00:20:13]>> Uh, so we actually had some piston to valve contact.

[00:20:16]>> Oh, yeah. from like cylinder three all the way back.

[00:20:20]>> We got a bad rod bearing.

[00:20:22]>> Well, funny you should say that. Watch this.

[00:20:30]>> Yeah, >> she is seized.

[00:20:32]>> Yeah. So, that's an indication there's not a lot of piston. Your piston protrusion, everybody. When the piston comes up, we don't have one here, but a piston and a diesel actually comes up above the deck. It actually you're squeezing about every every inch of air you can in these motors to get the compression ratio that you got. So when you have a bad it's good that you caught that. When you have a uh a rod bearing that goes bad, the piston will actually start hitting the cylinder head. So we that's why it's probably seized. Um you'll have to yeah take out what I can and Well, there's no uh Can you see a uh Where's your flashlight? a blackened rod. See how that rod's nice and clean?

[00:21:18]That one's kind of clean. See how black that one is?

[00:21:21]>> Oh yeah.

[00:21:21]>> See the difference here? See how dark that rod is? See that? Look how Look how nice and shiny. So that rod has got a bad bearing in it. Go ahead and pop the cap off of that one.

[00:21:31]>> Off of that one.

[00:21:32]>> Yeah.

[00:21:32]>> It looks like you've called it. Both of these center ones have. So let's just go ahead and get an extension or get in there.

[00:21:38]>> Yeah.

[00:21:39]>> I think you're going to need a half inch gun.

[00:21:42]Okay. I just got lucky.

[00:21:47]Okay, let's pull these off of here.

[00:21:49]Yeah, the rod string is actually spun.

[00:21:53]It's spun in the rod cap.

[00:21:56]Let's uh let's knock the piston out of there.

[00:22:00]Yeah, if we even can. Maybe we can turn a crank now. See if we can turn it now.

[00:22:06]Nope. Guys, we could have a main, too.

[00:22:12]Can we knock that piston forward a little bit? The rod might be in the way.

[00:22:22]>> Here's here's the bearing.

[00:22:28]>> So, the rods are going to be ruined, but let's uh let's disassemble it. Find out, you know, it's seized up because the bearings are seized, right? And let's see if it spun the mains.

[00:22:40]>> Okay.

[00:22:41]>> And uh but guys, all this so the first motor failed um >> two melted pistons.

[00:22:49]>> Two melted pistons. That's over fueling.

[00:22:52]>> Second motor had >> and and I'm sorry, the first motor also had uh fifth generation valve train issue.

[00:22:59]>> Yeah.

[00:22:59]>> Second motor >> primarily valve train >> valve train valve train issues. The third motor uh do we have valve train issues? uh only on two two push rods, two rockers.

[00:23:10]That was it. That's all I saw.

[00:23:12]>> Okay. So, it had it but not as the severity that the other motors had it.

[00:23:16]But this motor failed because of improper maintenance.

[00:23:20]>> Yeah. Okay.

[00:23:21]>> Guys, once again, the 67, great motor except for the val fifth generation, except for the valve train issue. But any motor, I don't care what it is, you don't maintain it, it's gonna bite