Killing NHC 250s -what we have learned killing 3 of them.

[JDToumanian]

A friend of mine was a truck driver back in the 1970s-1980s... I remember something he told me when he saw that I was installing a pyrometer in my deuce back in 2007. "You don't need that if you know how to drive!" He went on to say that you should never keep the accelerator pedal down to the floor, and always go up a hill in a gear such that if you did put your foot to the floor, you could still gain speed. He said if you're holding your foot to the floor on a grade, even if you're maintaining your speed and not lugging the RPM, you're over-working the engine. I didn't give much weight to that advice, but some years later, having put significant miles in trucks with pyrometers, including 8,000 miles in my deuce, I realized that he was pretty much spot on. If I kept my foot to the floor in the deuce, even just maintaining my speed, the pyro climbed dangerously high. Keeping a little reserve on grades like he said, the temps never go over 1,200.

Jon

 

[swbradley1]

Simp was just out at the farm last Sunday loading his 923 trailer with a 915 strapped down that Gimp and I helped load (amazing what my backhoe does).

That 250 of his sounded great as he pulled out to go down the road and turn around. Sounded good coming back too. Whatever he is doing must be working out for him.

 

[simp5782]

Simp was just out at the farm last Sunday loading his 923 trailer with a 915 strapped down that Gimp and I helped load (amazing what my backhoe does).

That 250 of his sounded great as he pulled out to go down the road and turn around. Sounded good coming back too. Whatever he is doing must be working out for him.

Even with a flat tire!

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[swbradley1]

Even with a flat tire!

Maybe THAT's what sounded good.

 

[simp5782]

Maybe THAT's what sounded good.

Better than gimp trying to drive the 915 into the bed of the truck.

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[74M35A2]

His engine does seem to run well. I would trust his judgement on NHC 250 PT pump work and fueling mods for sure, considering how many miles he has put on his vs the performance I saw his truck have. I was impressed with how well it took off with stuff in the bed and a big heavy trailer in tow.

I can't believe I just complimented a 250. Now I need to go take a shower...

 

[Csm Davis]

Okay so we have some data to go by, acme66 lost 3 or 4 engines. He says because egt in a stock engine gets to high when you floor it and hold it there in a 923 with 2000 lbs of people in it.
Okay in Vietnam they drove the 250 like a bat out of he'll by guy's that didn't have a clue when they got handed a truck and told keep up or die and they didn't have major issues and were loaded down and ran many times 24 hours a day. Oh wait he said this is caused by the automatic transmission.
Let's jump ahead to 1990-91 Desert Shield, Desert Storm these exact trucks maybe even his were driven over a million miles by the military and they didn't have major issues with liner failures.
All of these military examples are of young men and women who I love, but as I was one that age I know we did not treat these trucks nice. I am not knocking military drivers.
Now on to my hands I probably cut my teeth on a part from a 250 powered military truck, literally. When I was born my family moved houses for a living and used 5 ton military trucks exclusively, I have a picture of me in one at two years old, and the first time I drove one I was 6. I didn't get to go down the road until about 10 years old and then just back roads. At 16 I started working at Camp Shelby as a civilian during the summer and was given a military driver's license for most all wheeled vehicles up to the M916, which I drove to Keesler Air Force Base 3-4 times a summer. So jump ahead to about 2011 and I started as a contractor for Govliquidation using my wreckers to move 3500 M939 series trucks around and then help remove them from the base, so guys if you got one from Camp Shelby I probably was in your truck. Many days I have drove my 816's and 936's 20 miles down to the base worked it hard and then drove it home many days loaded with a 931 or 936 behind. I have always driven my trucks hard, I broke 4 wreckers in one week and none were engine failures, only 250 failures I have had were rod or bearing related. Acme66 I am not saying that you haven't had the problems that you listed. But I will ask how it is that your 3-4 are representative of the thousands of 250's that have been driven harder and over loaded more.

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[Mos68x]

Now I'm am not defending Acme66 or saying that he has or has not been at fault. However, for everyone of you that says these, and all other variants of trucks, were bulletproof and never broke down...were you the Army/Marine/Navy/AirForce comptrollers? No, I garauntee that absolutely NONE of you were, and only in the comptroller position would you really see how much trouble any of the service branches had with any of these trucks. Sure you might have worked with with in your unit, you might have even seen one getting worked on, or even better yet you might have worked in the motor pool and worked on some of these trucks. But remember one thing, only gives you LIMITED information to base your OPINION on. The only place where we would know how many engines died and maybe for what reason, is in the comptroller position. Only there would you see enough parts requests and spending to know the truth about how many of these engines and trucks did or did not die at the hands of any of the people in the armed forces. Yes I've seen some of these engines being worked on, does that give me any proper information to say it is gospel truth? Nope, not even close, and none of you do either! I have respect for many of you, but to attack someone because of consistent engine failure is absolutely rediculous. Y'all are no better than children fighting at this point, grow the eff up and be a part of the SOLUTION and not part of the PROBLEM. Like I said earlier, it very well could be that it is operator error but was I pointing fingers, not at all.

Just remember, no matter how popular some information or an opinion is, it is all still based on OPINION.

 

[snowtrac nome]

I operate snow cats and have a close network of friends that also run them where I'm at we are at sea level I get great performance out of my vw powered snow trac I also have a Thiokol 2100 with a turbo diesel ford engine in it. the diesel engine options were naturally aspirated at sea level and turbo charged for operation above 10,000 feet. my best guess is he needs a turbo at that altitude the thinner air with the same amount of fuel is going to cause heat problems at altitude

 

[Nomadic]

+1 for "don't attack the OP". I think he found a limitation of that vehicle. In looking at some of the LMTV's, there is an elevation limit stamped right on an engine plate (4,xxx feet). That could mean several things, like there is a limitation of the engine and maybe even there is a history of high elevation engine failures and that specification communicates what the design limitation is.

 

[JDToumanian]

In looking at some of the LMTV's, there is an elevation limit stamped right on an engine plate (4,xxx feet). That could mean several things, like there is a limitation of the engine and maybe even there is a history of high elevation engine failures and that specification communicates what the design limitation is.

At high elevations, the turbo can over speed because the air is thinner... I think they make these zippy turbos for emissions purposes, so there is less lag time, but their sensitivity to high altitudes is the down side. I don't think you can have it both ways, a fast, high boost, low-lag turbo that is also good to 8,000 feet. Not yet anyway.

Jon

 

[JDToumanian]

.....I have respect for many of you, but to attack someone because of consistent engine failure is absolutely rediculous. Y'all are no better than children fighting at this point, grow the eff up and be a part of the SOLUTION and not part of the PROBLEM. Like I said earlier, it very well could be that it is operator error but was I pointing fingers, not at all.

Maybe acme66 will beg to differ, but I don't think he's being attacked here... It's just that, unlike the LDT engines from a deuce, the Cummins 250 does not have a reputation for blowing up. Of course they can and do like any engine, but they are not known for it to be a serious problem. So to lose 3 engines under similar circumstances, something is up... operator error, previous abuse, bad rebuilds, or just bad luck. Maybe a combination? I don't own any running 250s, but the one in my M818 has a loud rod knock, which supports what simp says is a more common failure mode.

 

[98G]

I'm happy to have raw data from any and all sources. It's all about sample size. More is better.

My interpretation of the data may or may not match yours....

 

[simp5782]

My data is this. Green coolant isn't eating liners. He ran ELC, it eats rubber which compromised his Orings on the liners. which caused a leak. If you burn a truck up from putting your foot in it too much regardless of a pyrometer or not it is your own fault. Especially one that is not turned up. Like JD said you don't have to be all the way in it to get your power. I remember the first thing Wreckerman ever said to me about an old 250 engine was. "She does best about an inch or so off the floor. she pulls well. Otherwise shes a pig" and that's all she has to say about that. All the old timers on here always have mentioned in the "getting more power out of a NHC250" threads that you have to keep your foot out of them if you are going to run a hot engine. Especially if you have not metered the pump right.

1 engine with a bad bearing yeah understandable, maybe 2 but 3 all of which have the same issue screams that its operator or maint error. I don't have a problem pointing it out to someone. But since this engine he is on now was 100% put together by the OP we can see how long it lasts before its the engines fault or the operators fault. Who knows. hopefully she will run a million miles.


What antifreeze equivalent does the TM say to use? I am not a TM preacher but could be a giveaway as to what is appropriate.

 

[Nomadic]

What is ELC?

 

[simp5782]

What is ELC?

Extended Life Coolant.

 

[74M35A2]

VGT turbos make a good attempt at giving the best of both worlds.

Coolant eats bearings quickly, like pouring acid on them. You may also be onto something with altutude if the PT pump does not reference atmospheric pressure. Pretty old technology, so I doubt it does?

8.3's have blowers stock, and don't commit suicide too often. Try a batch of those next and report back.

 

[Csm Davis]

Now I'm am not defending Acme66 or saying that he has or has not been at fault. However, for everyone of you that says these, and all other variants of trucks, were bulletproof and never broke down...were you the Army/Marine/Navy/AirForce comptrollers? No, I garauntee that absolutely NONE of you were, and only in the comptroller position would you really see how much trouble any of the service branches had with any of these trucks. Sure you might have worked with with in your unit, you might have even seen one getting worked on, or even better yet you might have worked in the motor pool and worked on some of these trucks. But remember one thing, only gives you LIMITED information to base your OPINION on. The only place where we would know how many engines died and maybe for what reason, is in the comptroller position. Only there would you see enough parts requests and spending to know the truth about how many of these engines and trucks did or did not die at the hands of any of the people in the armed forces. Yes I've seen some of these engines being worked on, does that give me any proper information to say it is gospel truth? Nope, not even close, and none of you do either! I have respect for many of you, but to attack someone because of consistent engine failure is absolutely rediculous. Y'all are no better than children fighting at this point, grow the eff up and be a part of the SOLUTION and not part of the PROBLEM. Like I said earlier, it very well could be that it is operator error but was I pointing fingers, not at all.

Just remember, no matter how popular some information or an opinion is, it is all still based on OPINION.

No I was never the comptroller but I never said the 250 is bulletproof and I didn't just look at one engine and base my argument on just that. I Wil say that i have probably worked on and fired up around 3500 Cummins 250 engines and also privy to the engine shop operations and friends with the technicians running it, which is why I have not turned up a 250 in any of my trucks. They also told me of many pumps that were turned up and damaged the engines most of which were bearing and rod damage, not all, as there were definitely melted pistons and liners. My biggest problem with the 3-4 engines melted is I don't see that acme66 has had his pumps rebuilt or even checked to see if they are correct, which if I melted more than one engine would be my first stop. I do hear him say cavitation is not the problem but continued to use a antifreeze that according to some will eat o-rings and that could be the problem. Or his driving or his trucks could have just been those trucks. 10 burned engines would not be a large enough sample to decide that all 939 trucks will do this. Maybe we can get Simp to go drive the tour for a while.

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[someoldmoose]

Heard this was a HOT thread, so here's an Old Farts hot air. :

1 - IF you have never had experience with TUNING a mechanical diesel. Or if you have and still like to know what your engine is REALLY doing, GET AN EXHAUST GAS TEMPERATURE INDICATOR. EGTs are the "chalk check" for the engine that I PREACH about for tires. There is ABSOLUTELY NO BETTER indicator of what your big, bad girl is doing under the covers. NONE ! ! ! Most of "us" are hobbyists with little experience in Heavy Engine use and tuning. A "Pyro" gauge will save you from many, many tears and spent dollars.

2 - The only thing MORE important than knowing what temp. yer EXHAUST is would be knowing that your COOLING SYSTEM is sufficient to handle that HUUUUUUUGE amount of thermal flux these monsters create. Foot on the floor for a THOUSAND MILES, or "idling" through the local Parade du' jour. If she can't get rid of the heat, she's DEAD. Just a matter of time and THAT is a FACT. ELC was created to extend the coolant life of MODERN automotive engines for the ree rees who think Auto Maintenance is putting gas in the tank and a Burrito in their FACE. When was the LAST nhc / ntc 250 built ? Long before Dex-cool came around. Stick with the OLD GREEN ETHYLENE. Change it as directed, or even more often if yer components are original, OR add a filter system ( MY CHOICE ) AND change it as directed. The anti-corrosion package has a FINITE lifespan whether filtering or not, it MUST be refreshed. If ya wanna run an ALTERNATIVE COOLANT, use clean distilled water with Royal Purple ICE (trademarked) additive. We run this in 8000 HP engines because we aren't allowed to dump EG coolant on the track. It works WONDERFULLY. We also dump the entire cooling system during EVERY rebuild. Expensive ? Maybe, what's a 250 rebuild kit cost nowadays ? I don't wanna find out if I can avoid it.

3 - Air, Air, and MORE AIR. THE ABSOLUTE FIRST THING I am doing to Exit Strategy is to find a K & N filter that fits and installing it. Keep it clean and let her BREATHE. Asthma and Diesels do not co-exist. If she has the same amount of fuel all the time, and the available air keeps dropping, she's gonna BURN. How will ya know ? SEE point # 1, end of story. Restriction gauge is for knowing who to blame ( I M H O ) when the motor melts down. " Oh, you didn't see the restriction gauge went red ? Enjoy working for someone else. " Your Pyro gauge will tell you LOOOOOOOOOONG before the restriction gauge. If mine even MOVES it's too late for filter service to me.

4 - And summation, I respect all who post here. We have it ALL folks. I bet if somebody did the math that there is WELL over a Milenium of experience here. BUT we also have people buying these MONSTERS who have never driven / owned / leased / borrowed anything bigger than an Impala and probably had the garage doing all their services. THEY are the ones we ( the "experienced" ) need to coach, guide, and help prosper because guess what . . . They bought an MV whether it be a Mule or an M1A1 that they found on FleaBay. They found out what the COOL kids really play with and decided they WANT one. It's our RESPOSIBILITY to proctor them and make sure our Hobby gets to remain one. Driving ANYTHING, ANYWHERE is a PRIVILEGE, NOT a Right. There is NO Amendment regarding the Use of Automobiles for Commerce or Pleasure. Our States ALLOW us to have these JOY BRINGERS IN OUR LIVES. Let's respect that, AND each other, ALWAYS.

Thank you Ken, Wes, Robb, Jeff, Leon, and all the others whose names elude me ( Rustystud ) or whom my fingers are getting too tired to type. We ALL have soooooomething to bring to this Party. So LET'S PARTY. Moose Joose all around !

Best wishes and Luck to ALL & Happy Motoring ! ! !

 

[Suprman]

Maybe his drivers dont want to floor it due to noise and smoke since he has passengers in the bed. Just give it enough pedal to go. I have a habit of flooring the 250 if I am driving one.