Changing out the coolant on the NHC250

[acme66]

Lots of talk of changing out the coolant on the NHC 250 because of liner failure. Well I have done that with three different motors so far and I just lost the third one today. If it was on your to-do list just put it off for a bit. I am at 100% failure the year after making the switch, all look to be dropped liners. That includes a truck bought from a logging company which was used much harder than I have been using it yet I am the one the liner craps out on. If you are reading this later than May of 2017 just email me acme66@yahoo.com and see what I found out. I am starting to think that the ELC coolants are attacking the o-rings or maybe they are dissolving all the happy little rust particles that are keeping them sealed up. Maybe it is nothing to do with the coolant and I have just been that unlucky but the pattern is so precise between each of them. Let alone miles, this one failed 300 yards from the exact spot the first one died. Just give me some time to figure out what is happening. My thought right now is wait on the coolant swap, let's use my trucks as the test case.

In other news if someone wants to share a beer and let me cry on their shoulder for a bit that would be cool. I am not sure the company can eat the cost/time of a third lost motor and now I worry about how long they are going to last even if I rebuild them. People say a school bus motor will not have the grunt to do the job but then that also say the 250 is a rock-solid reliable workhorse. Tonight I am just sort of twisting in the wind.

Ken

 

[71DeuceAK]

Interesting to know. Good luck, Ken, I hope you get things sorted out. IF I was in MT I'd let you cry on my shoulder but I'm in Alaska, LOL.

 

[rhurey]

Curious... Did you add filters when you changed the coolant? I'm assuming you haven't torn any down yet to see if it was rings or liner eat through...

 

[162tcat]

I'd be interested to see the results of a tear down on these.


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[acme66]

One has been torn down, the liner did not eat all the way through but the pitting did extend under the first o-ring and we confirmed it was leaking past the rings. All of the rings were very swollen and sticky but the liner also showed signs of heat damage. Not sure if it was heat or oil/coolant damage.

Ken

 

[therooster2001]

What coolant did you put in? Assuming an ELC as stated, but which brand? ELC and SCA's are different animals. And dude, that's some crappy coincidence. Bummer...

 

[162tcat]

We're all of those m939 series trucks?


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[acme66]

All three were m939 A1 trucks with the 250. I can come back with brands in the morning.

Ken

 

[71DeuceAK]

It would be interesting to know brand names, maybe brands to avoid. Can you tell us the other circumstances surrounding the failures? I'm a lawnmower-spark-plug mechanic myself still and have a lot to learn but I'm sure others might be able to pinpoint nuances.

 

[gimpyrobb]

Did you measure the PH of the coolant? Too much elc/sca is just as bad as not enough.


Edit, It really sucks to hear this. If memory serves, you use these to make money for your family. I hate to hear small business owners struggling.

 

[acme66]

Did you measure the PH of the coolant? Too much elc/sca is just as bad as not enough.

Measure it no, just mixed it asper instructions for the temps in our area. The coolant was one year old exactly at this point. It was the good "lifetime" stuff recommended for OTR trucks. Short of dumping in battery acid I don't see one year of a ph imbalance is eating through liners. If I remember correctly one of the trucks was filled with the factory 50/50 mix and it still did the same thing, might have been this one. This isn't a case of big simple issues, something is causing liner failures one year after coolant change (it still might not be coolant) it has to be more complicated and the sticky o-rings has me leaning towards compatibility issues with the old parts. I just think that for the moment if you have a 250 and were due for a coolant change I would go with a fresh dose of the cheap green stuff and wait to see for a bit prior to mixing modern chemicals with old parts.

Ken

 

[red]

Did you go with the green, red, or grey coolant?

 

[acme66]

Red. Used the brand recommended by the local heavy engine shop as what they would run in that truck/motor. I will try to look up in my records exactly what brand.

Ken

 

[red]

Any film or sludge material in the cooling systems of the other engines? Red and green don't mix well and have some bad chemical reactions.

My wrecker has green in it.

 

[acme66]

No sludge but I would get a bit of rust colored gunk out of the rad drain each time. That was same with all three both before and after the change. At the change over I flushed and ran them on hose water several times until it drained colorless and clean then I emptied everything I could get and refilled using distilled water for any mixing. Two different hose water locations, one municipal water, one well water untreated, same result 3 times. I will try to post pictures of the gnarly o-rings and get opinions if the swelling was caused by reaction, heat, age or??? The motor I lost today has now been sitting for two hours and the oil level is about 1 inch higher than when I checked it prior to driving. Probably drop pan tomorrow and my prediction is to find one hole where the piston briefly seized to the liner streaking it with aluminum and that that hole will be the one with a weepy liner. First truck it was #5, the second was #1 I am going to guess #4 this time, I just has me a feeling.

Ken

 

[71DeuceAK]

Think it'll be any easier of a fix this time? I've been following your videos of rebuilding the one motor on YouTube, lest I ever have to do this in the truck I have a line on ('84 M923).

 

[simp5782]

I use the walmart must add water green coolant and distilled water. 70/30 and two bottles of the sca additive

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[simp5782]

Did you use your voltage meter to see how much energy your coolant has? A simple bad ground can cause enough electricity in the coolant to eat thru a liner. I had several navistar engines that had electrolosis.

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[Scar59]

I use the walmart must add water green coolant and distilled water. 70/30 and two bottles of the sca additive

Yep, keep it simple, also get the PH test strips to keep SCA additive spot on.

 

[simp5782]

On another note if it was s truck those Thompson river road loggers drove around it probably was filled with creek water. Or even worse. Spring water

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