305HP H.O. engine, what is Cummins life expectancy / actual life expectancy?

[Coalsmoke]

hey guys, I was reading a thread here on the TDR about a downed engine, and someone mentioned that the 04 24V engines had a Cummins rated life expectancy of 350,000miles. I find this hard to believe. I'm aware that power mods can/will shorten the life of an engine, but what about the stock figures. Isn't this essentially still the same ISB configuration as the 2nd gen 12Vs and should it be closer to 1 million miles?

 

[FourBarR]

I believe that 350,000k is Cummins estimated life before overhaul. This would be for a stock engine. There are lots of 1st. and 2nd. gen with a lot more miles on them.

 

[Coalsmoke]

Yeah, that's what I was thinking too about the 12vers and that's what had me scratching my head. 350,000miles is 560,000kms. I'm at 412,000kms right now and am in excellent shape, in fact my oil analysis shows a trend of the engine getting slightly better since I've owned it. Maybe the 12v engines are also supposed to be overhauled at that point too, just that they are generally under worked in these light truck applications and can go quite a bit longer?

 

[betterthanstock]

350K is average based on school busses, trucks, etc...

Stress, oil, dust, heat, cold, fuel quality, all make a huge difference in life expectancy. And that's to first overhaul. What's and overhaul? A valve job? Short/long block? Injectors/pump?

 

[Gary - K7GLD]

Life expectancy *averages* in engines is like lifespan in humans. A baby dies at birth, the father lives to be 100 - the "average" between the 2 is 50 years - but ONLY an average.



Here on this board, we've seen our share of extremely high mileage engines - but ALSO a few that failed at quite low mileage, and a maker has to consider the SPREAD of potential lifespans in establishing a public statement as to life expectancy.

 

[Coalsmoke]

Good point guys about the averages. I was looking at it too much as a probable milestone instead of as an average.

 

[WPeschel]

Watch them valve seats... I think I dropped another vavle seat...

 

[cerberusiam]

If you dig into Cummins reccomendations, I think the 350k is a health check point. They run a set of tests, compression, leak down, etc, and if they are within a predetermined range you are good to go for another 350k or something feels wrong. Leastwise, thats how it was explained to me.



Life expectancy is more of a mean than an average. There are too many variables that influence it.

 

[Coalsmoke]

WPechel, valve seats? I didn't know they could go anywhere unless you pressed it out. What's the story on that?

cerb. that makes sense explaining the 350K interval as it being a check-up.

A mean is essentially an average, do you by chance mean the median? In terms of engine life expectancies, I think perhaps it might be best described as more of a natural distribution but a person should adjust for outliers then to get a better idea of the norm.

 

[WPeschel]

WPechel, valve seats? I didn't know they could go anywhere unless you pressed it out. What's the story on that?



cerb. that makes sense explaining the 350K interval as it being a check-up.



A mean is essentially an average, do you by chance mean the median? In terms of engine life expectancies, I think perhaps it might be best described as more of a natural distribution but a person should adjust for outliers then to get a better idea of the norm.

You might do a search on dropped valve seats... I dropped the valve seat in number on piston about a year ago... My truck is knocking again only 5 months after getting it back from the shop... The mech I used took a head to a machine shop and had them cut the seats out and install new ones with supposedly tighter specs...

 

[RMalone]

One other thing to keep in mind. Other than people who make a living driving their trucks long distance, almost no one keeps pickups for 300,000+ miles. Construction type guys usually trash the rest of the truck long before then and most daily driver and recreational tow types get sick of the truck before 300k.



I mean think about it, if you drove 50,000 mi/yr (pretty high miles unless your long hauling) it would still take 20yrs to hit a million. The 1989 model year (the first REAL diesel truck) is about 20yrs old right now. As far as I'm concerned if you can get 10yrs and 300,000 mi out of a truck you've done real well.

 

[Coalsmoke]

You might do a search on dropped valve seats... I dropped the valve seat in number on piston about a year ago... My truck is knocking again only 5 months after getting it back from the shop... The mech I used took a head to a machine shop and had them cut the seats out and install new ones with supposedly tighter specs...

Thanks, I've been reading. Seems like a lot of people are having issues, but more or less it seems to also be those running higher EGTs. Thanks again, I'm still reading about them, I'm a little surprised that they don't have a safeguard designed into them such that if they were to become loose, they wouldn't necessarily drop. But, pay to play, right.

One other thing to keep in mind. Other than people who make a living driving their trucks long distance, almost no one keeps pickups for 300,000+ miles. Construction type guys usually trash the rest of the truck long before then and most daily driver and recreational tow types get sick of the truck before 300k.



I mean think about it, if you drove 50,000 mi/yr (pretty high miles unless your long hauling) it would still take 20yrs to hit a million. The 1989 model year (the first REAL diesel truck) is about 20yrs old right now. As far as I'm concerned if you can get 10yrs and 300,000 mi out of a truck you've done real well.

Yep, I agree completely. I was just used to driving the 12V and never thinking about accumulated mileage and until I came across that mentioned thread and it got me thinking about what differences were in place lowering the lifespan. However, I'm thinking, as pointed out above, its still the same lifespan, just applied differently. More fuel / more power = shorter time to overhaul, and, if 350,000miles is the overhaul point then a person should be in pretty good shape for a long time.

 

[rbattelle]

If you dig into Cummins reccomendations, I think the 350k is a health check point. They run a set of tests, compression, leak down, etc, and if they are within a predetermined range you are good to go for another 350k or something feels wrong. Leastwise, thats how it was explained to me.

That sounds logical. Don't forget a valve clearance adjustment.



Ryan

 

[ChrisKringle]

I think mine needs a new carburetor already

 

[cerberusiam]

WPechel, valve seats? I didn't know they could go anywhere unless you pressed it out. What's the story on that?



cerb. that makes sense explaining the 350K interval as it being a check-up.



A mean is essentially an average, do you by chance mean the median? In terms of engine life expectancies, I think perhaps it might be best described as more of a natural distribution but a person should adjust for outliers then to get a better idea of the norm.

Yeah, median not mean. The nerve impulse left the brain saying "median" and the fingers were defaulted to "mean". I think my CAN Bus has communication errors. :-laf:-laf

 

[Vaughn MacKenzie]

Have 408,000+ on my '96 but the engine could use a refresh, definitely showing the signs of fatigue. In the years on TDR I've read of a few cases of tire engines by 200k to 300k, sometimes though it's guys just wanting to build something capable of handling more HP versus really needing an overhaul.

Then there's those that do crack a million miles, seems they're ones running stock power and operate under ideal conditions (few short trips). The highest miles I knew of firsthand was 1,240,000 on a '90 2wd with no engine work other than the injection system.

Vaughn

 

[Coalsmoke]

Vaughn, that's impressive.

Yeah, median not mean. The nerve impulse left the brain saying "median" and the fingers were defaulted to "mean". I think my CAN Bus has communication errors. :-laf:-laf

No worries, I hear you on the communication errors.

 

[Tinman]

I thought that 350K number was recommended for sever duty like UPS trucks. The pickups have a much lower duty cycle and less abuse than delivery applications. Of course, the more HP and harder one drives, the higher the duty cycle and short time to rebuilt. I think there are some fairly hight hp trucks around here with pretty good mileage on them. The high HP marine versions of these motors give a duty cycle in their ratings. I believe the CR marine version goes up to 425 HP, but is rated to run at WOT only 20% of the time. I'd be interesting to know what the overall recommendation on that motor is. Ask you self, how often are you at 425hp in your truck engine? Even at increased HP, these truck engines can go a long time if maintained well and drive sanely.