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ELC is bad juju for old engines. Rubber parts WILL be compromised. Stick with a low silicate, normal glycol antifreeze.
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This is why I fuss about guys changing to fluids that have never been used in these trucks, some of you folks over think this stuff. These trucks were designed before most of us were born, (KISS) keep it simple stupid is the thing to remember. If it was good enough for 50 years of military use it should be good for us to use, I am not saying not to put the newest latest greatest junk in but be prepared for what might happen if it is incompatible with 50 year old rubber.ELC is bad juju for old engines. Rubber parts WILL be compromised. Stick with a low silicate, normal glycol antifreeze.
Okay whipper snapper little educational information the M939 came from a long line of great trucks that started in 1951 with the M39 trucks then the M809 trucks in 1969, then the M939 in 1982. And each of the newer series got the first trucks made from the older series trucks so I don't know if this actually happened but you could have possibly have a M939 made from a M39! Doubt that ever happened but I have seen stranger things. So it is very possible to have a 48 year old 250 Cummins in a M939. Supposed to have been 11,000 M809s upgraded M939 so I bet there are some old motors running around still.Keep us posted Ken! I saw your latest 4 updates on YouTube, great videos! Re: the 50 year old rubber, the 939's are more like only 25-25 years old, but yeah, I know what you mean. Still before some of us younger enthusiasts (like myself) were even born...
Dude, if you have the tools and can time it WHY would you take it to a shop to set the overhead?We will time it as per the manuals but then take it to a trusted heavy truck shop to have them run the full top end.
Cummings.
Ken
Dude, if you have the tools and can time it WHY would you take it to a shop to set the overhead?
And it is Cummins.
Cummings, she was a **** star, Carol Cummings. http://www.imdb.com/name/nm0191860/
Out of curiosity, what are your EGT's at and for how long?Truck is back up and running. Used liner, piston, wristpin, rings and we reused the rod bearings that came out of it. Started instantly and after smoking for a bit burning the grease off now idles with no hint of white, black or blue smoke. Rolls a little dark grey when reved up, more than I remember it doing before. Has a bit of blow-by (one would expect that with a mix-n-match set of used rings) but less than the motor we are currently rebuilding did in its prime. If I had just inspected the motor for the first time with that puff of blowby I wouldn't have given it a second thought. Ordering in another full kit then driving it as is up to the shop (80 miles) to put the inframe in. Working on dumpster picked sheets of plywood in the dirt isn't fun. Also going to put a full injector set in. We will time it as per the manuals but then take it to a trusted heavy truck shop to have them run the full top end. Motor runs so smooth I can't think the timing is off far enough to eat pistons but at this point I am checking off boxes. I really, really expected to see pitted liners, almost kind of wish I had... Since everything we found in this motor was brand new (or nearly so) I am going to save it and dump it into the very first truck to die under us. Maybe I get away with just buying a gasket set. If these things are just going to randomly explode then why have it randomly explode with $2000 worth of new parts inside?
Back to the coolant:
Motor has a build date of 1985 as per serial number check with Cummings. Scrap motor I just bought from a 70's 808 truck had a build date of... 1987. I have a chunk of gasket in undiluted coolant, one in mineral spirits and a chunk in lacquer thinner. If those two solvents don't touch it then we will know it wasn't the coolant but I have the control test anyway. Also plan to cook some to see if heat makes them gummy. Some truth to the old motor, old fluid argument but then it isn't an old motor and there is a iron clad reason why a 100,000 mile motor when I was a kid was about done for and today it means only 30-40% of the expected lifetime. There is a reason why million mile heavy OTR motors are no longer a few and far between event and have become, maybe not expected but very, very plausible in even moderate maintenance situations despite much higher HP and boost. Modern fluids and filtering. Period. What I am using is the exact spec (or one of anyway) recommended by the manufacturer for that motor with that build date. But something keeps shooting the horses out from under me. At this point I am trying to eliminate the coolant. Finding 100% spotless liners in that truck wasn't what I expected to see. I expected pitting. I know for a fact pitting was in the other two but this looks spotless... so why did it fail? Gummy spots in the o-rings on this one were located at 90 degrees to the crankshaft. That is where the liners wear the most and the location one would assume heat might build. I don't remember where the gummy spots were on the other motor by my father is quite sure they were also at 90 degrees to the crank. It is like the 5 ton towbar thing, I am sick of what if's and guesswork so I plan to systematically torture those little rubber rings until I know why they failed and if they were the cause of all my grief or tragic victims in some other set of circumstances... and then I will tell you what I found.
Ken
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