55Mph Detonation. . .

[Srjeeper]

FMJ, that certainly is not the case on this end.....just passin on what took me 46 years (36 as a owner/operator) to pick up.

I don't know what happened to your or anyone elses motor and none of my postings were intended to suggest I did.

 

[mudguppy]

... This turning into a "I told you so thread"

yes, as has every other 'blown engine' thread as of late - you were either abusing it or running it at 15,000+ rpm. and if you prove that you didn't, well, then it must have been abused by 'Soldier A', because no one here will accept that the multifuel motor is anything less than the most reliable and bestest designed engine ever.

yep, this was clearly your fault since it was in your possession.

 

[stumps]

So I was all good at 55?. . .

Apparently not.

Until a better explanation for the rods being thrown at 55 MPH comes along, I think 50 MPH in 5th HI is a pretty good maximum speed for --my-- deuce. I hope I am right.

You have done the experiment with your Toole rebuild, and the result you received was very sad. Others have done the same experiment and had good results... lots of others. Maybe your next engine will take it better.

It will probably only cost you a couple of engines to find your tolerance level.

For now, I am going to take the lessons of your misfortune with your Toole rebuilt engine and use it as a pretty good reason to take it easy on my Toole rebuilt engine.

-Chuck

 

[cranetruck]

Reading this with a great deal of interest....the thread is bogging down a bit, so I'll try to contribute with some things to discuss.
We need to correlate the hour meter and the odometer readings. Too bad they are not on the same instrument, but if we assume that they have been together for the life of the vehicle, then we can get an average speed and it's very likely going to be very low. The trucks were idling a lot.

A military vehicle is designed for a long life (20 plus years) and may sit unused for long periods of time, but must be up and running on short notice.

I have put six or seven times the mileage on my deuce compared to what it had accumulated during its service life. It was a fuel tanker and apparently not driven as much as the cargo versions. About 3,000 miles in 20 years.
My hour meter is showing over 1,400 hrs. Note that the hour meter runs a different speeds for different rpm, low rpm, less hours registered.

After getting fuel in the crankcase oil, my multi started to develop a "knock" and very low oil pressure after the oil warms up, in the order of 5 to 10 psi.

Questions:

Can somebody elaborate in detail on what creates the mechanical "knock"?

My 8x8 multi (LDS465-2) features pistons with a 5th ring near the skirt, in what way does that allow higher rpm, if not by itself, but how does it contribute, less flopping around?

In the case discussed in this thread, were there any, precursers or indicators, oil analysis result(s)?
In my case, the oil analysis results show an increase in wear metals as the oil pressure drops.

I have not managed my crankcase oil very well and am now paying for it. In contrast, the 8x8 oil has been changed twice since I brought it home and it hasn't been driven much at all. It also has a bypass filter installed, all to prevent the problems I'm having with the deuce.

I also read somewhere that straight 30W oil is equivalent to 20W50 oil, so we may need higher viscosity oil when using the multigrade oil.

Just a few more things to toss around...

 

[mudguppy]

Bjorn, my opinion:

rings do not provide stability for a piston, they are the method of compression/combustion sealing and for cylinder wall and/or piston oil control.

also, where did you read that 20w50 = 30W? because, by definition, 20w50 = 20W when cold + 50W when hot.

and a mechanical knock is a bearing and/or clearance issue. likely, after your oil got so diluted from the fuel the bearing may have experienced excessive wear. the knock you hear under low oil pressure is this [new] gap in the bearings. higher oil pressure provides more oil to 'cushion' and calm the knock, but the clearance issue could still be there.

 

[FMJ]

yes, as has every other 'blown engine' thread as of late - you were either abusing it or running it at 15,000+ rpm. and if you prove that you didn't, well, then it must have been abused by 'Soldier A', because no one here will accept that the multifuel motor is anything less than the most reliable and bestest designed engine ever.

yep, this was clearly your fault since it was in your possession.

LOL, well, I guess since I was driving it. . . .

Funny thing is, I have a sister to this truck, 0539-14469, the one I was driving was 0539-14467, both rebuilt at TEAD in 90-92ish

For now I think I'm going start driving it, and see what happens. . .

Ed

Sorry about the previous post, I was a bit "fatigued" last night

 

[FMJ]

I was running rotella 15w-40 oil pressure was normal, until the "event" , changed about 2000 miles ago, and checked before I rolled out, was 2 qts low so I topped it off. motor was smooth with no abnormal noise until the grenade murphy planted went off. . .

 

[stumps]

...

After getting fuel in the crankcase oil, my multi started to develop a "knock" and very low oil pressure after the oil warms up, in the order of 5 to 10 psi.

Questions:

Can somebody elaborate in detail on what creates the mechanical "knock"?

It is pretty simple really.

The oil pump feeds pressurized oil into each bearing. The oil flowing into the bearing fills the gap between the journal and bearing, and acts as a cushion to to absorb the shock loading of the bearing. Under normal bearing loads, this oil cushion prevents metal to metal contact from ever occurring.

If the oil is too thin, its viscosity is insufficient to prevent the oil from flowing out of the space between the journal and the bearing during normal bearing loading, and the journal is allowed to strike the the bearing at peaks in the bearing's loading. This makes a knocking sound. It also causes the relatively soft bearing material to be hammered out of the bearing, permanently increasing the gap between the bearing and the journal. You see this result as a lowering in your oil pressure, and you hear it as a continuous knock-knock-knock sound as your engine does its work.

You can gain some additional engine life, after this sort of abuse, by going to a higher viscosity oil. Higher viscosity oils can fill larger gaps between bearings and journals without being squished by the high bearing loads.

All is not wonderful, though. The higher viscosity oil may be too thick for the other lower load bearings in the engine.

My 8x8 multi (LDS465-2) features pistons with a 5th ring near the skirt, in what way does that allow higher rpm, if not by itself, but how does it contribute, less flopping around?

A ring can only act as a seal. It is the clearance between the piston and the cylinder wall that prevents flopping around. The rings float in the piston's ring grooves.

In the case discussed in this thread, were there any, precursers or indicators, oil analysis result(s)?
In my case, the oil analysis results show an increase in wear metals as the oil pressure drops.

I have not managed my crankcase oil very well and am now paying for it. In contrast, the 8x8 oil has been changed twice since I brought it home and it hasn't been driven much at all. It also has a bypass filter installed, all to prevent the problems I'm having with the deuce.

I also read somewhere that straight 30W oil is equivalent to 20W50 oil, so we may need higher viscosity oil when using the multigrade oil.

The first number in SAE engine oil designations is the viscosity of the base oil used to make that particular grade of oil. The second number is the effective viscosity at 210F, and is due to the additive package used in making the oil product.

When the oil is new, and the additive package is functioning properly, the base oil viscosity is only important to the starting of a cold engine. Once the engine warms up, the additive package's contribution to the oil viscosity is what is important.

A 20W50 product will be much thicker than your bearings were designed to use at normal operating temperature. It will also make starting when cold more of a strain on the starter motor, and the oil pump, than will 15W40.

-Chuck

 

[cranetruck]

......
also, where did you read that 20w50 = 30W? because, by definition, 20w50 = 20W when cold + 50W when hot.
.......

That finding goes back a while, just did a search on Google and found this among other hits (from thunderpress.net):

"It’s a sad fact, the SAE grading system has consisted solely of a check on the time taken for a measured volume of oil to flow under gravity through a small orifice in a piece of laboratory glassware known as a viscometer. Testing monograde oil this way is valid enough, but it’s pretty much accepted by oil experts that, to some extent, viscosity-improving additives in modern multigrades only serve to “fool” the test equipment. The flaw is, no account is taken of the viscosity improver thinning due to shear load. When multigrades were first introduced in 1951, the notion was that (for example) a 10W/30 would work in place of straight 30W. After all, it met 30W viscosity requirements in the viscometer tube! It didn’t quite work out that way and today we consider the (more or less) correct multigrade equivalent of 30W to be 20W/50."


I have no personal opinion on this, not knowing the chemistry and my oil analysis reports show fuel pollution and therefore lower viscosities, however,
I use straight 30W in both the deuce and 8x8 multies (except when changing oil in CA during my cross country trip when 15W40 was used).....

 

[stumps]

I look at it this way, a heck of a lot has happened in the oil world since 1951. Back in 1951, gasoline and diesel engines were frequently ready for the scrap heap well before 100,000 miles. Today, it is common for a gasoline engine to go 300,000 miles, and it is extremely common for light truck diesels to go 500,000 miles. Some even make 1,000,000 miles. All using multi viscosity oils.

The flaw in the argument made by the quoted author is shear load testing is a standard part of all oil testing.. along with 2 or 3 dozen other tested attributes. These tests show up in the two letter code that every motor oil made today carries (eg. SJ, SK, ... CG,CH,CI,CJ, ...). As new tests are determined to be necessary, a new code is provided for oils that meet the tests.

There are some diesel manufacturers that specify straight weight oils for some of their engines. DD is one. They specifically forbid multi-viscosity oils in their old 2 stroke diesels. I consider that more an indicator of unique oil needs for the 2 stroke engine, than a condemnation of multi-vis oil.

Every 4 stroke diesel engine manufacturer recommends multi-vis oil use in their engines. Virtually all recommend a 15W40 oil for climates with a moderately cold winter, and moderately hot summer.

-Chuck

 

[steelandcanvas]

I'll tell you something I'm going to do different....This time we do oil analysis....Maybe this would have given me a heads-up to the eminent failure.

 

[stumps]

I'll tell you something I'm going to do different....This time we do oil analysis....Maybe this would have given me a heads-up to the eminent failure.

It would certainly be worth doing, but I don't believe these rod problems have anything at all to do with the oil. I need to see a few bearing shells. I need to see some caps. They should tell more of the story.

Purely a quasi educated guess, but I would say with pretty good certainty the problem is fastener failure on the rod bolts... and yes, the engine speed was part of the problem, but might not have been an issue with top quality bolts installed properly.

One guy on the assembly line at Toole that, "Didn't need no stinking torque wrench!" could have over torqued thousands of rod bolts over a several year period. One guy that always listened for the wrench to click, and then cranked the nut another 1/4 turn for good measure, thousands more... Take these mistakes, and salt them among all of the SS guys that own deuces, and want to get on down the road at 55, and it could look like a grenade went off in our ranks.

Every one of our engines that throws a rod makes dozens of guys shake in their boots.

But to know, what is really happening, we need to see some bearing inserts and rod caps from thrown rods.

If the problem is oil related, the soft bearing metal on the inserts should be smeared across the insert. The caps should be torn on the leading side, and bent on the trailing side. IF it isn't like that, we can stop talking about oil problems.

-Chuck

 

[steelandcanvas]

Chuck there is alot of Guys wanting to get to the bottom of this, me and FMJ especially. I don't plan on tearing the motor down real soon, this breakdown gives me an opportunity to do some refurbishing, painting, seals, tires, and other tasks that are put off during the parade/event season. However, and I've said this in another thrown rod thread, as soon as I tear into it, I'll have some real good photos and a narrative of what I find.

 

[clpo]

Sorry for the failure FMJ. My Avatar shows the result of a very similar failure under very similar circumstances. I have not torn down the old engine to try to learn more yet, but I had the same hunch about rod bolt failure that Stumps mentions above. Wish there was a way to know for sure. Everytime I get in and start up my new MF, I wonder how long 'till it happens again?? In now pay little attention to the speedo and live by the tach and 2300 RPM.

 

[OPCOM]

Sorry to see this! I note the rebuild was not punched out, stock sizes. seems like the may have done the sleeves, new crank, and all. I hope they did not re-use a bolt..

 

[OPCOM]

yep, this was clearly your fault since it was in your possession.

that reasoning did not work well when my friends allowed my generator trailer to burn to a crisp. At least you broke your own stuff instead of someone else breaking it for you.

 

[cranetruck]

Thanks Chuck for your insight!

Looks like a quality control problem based on what we have to look at then.

Discovered a hardware "missuse" about six years ago when I changed the front axle seals on the deuce. The nuts (twelve on each side), holding the spindles to the axle housing were of an inferior grade and could have let go at any time.
The nuts were so soft that the threads were stripped and they could easily be scribed with a screwdriver!
Here is part of the communication with CGarbee, who hardness tested one of the nuts:

"Anyway, the Rockwell C numbers for your nut have a mean of 6.7 with a std
deviation of 5.4.
For a grade 3 nut, the mean is 10.4 and the std deviation is 3.0.
For a grade 5 nut, the mean is 14.4 and the std deviation is 1.2.
For a grade 8 nut, the mean is 15.1 and the std deviation is 1.9"


"Hi Cabell,
Thanks for doing the test!
Did I explain where these nuts were used on the deuce? Well there were 12 on
each side holding the spindles to the front axle. When I took them off
several were stripped from being "overtightened" on the #8 studs. Most were
deformed like the one I sent you.
I called Rockwell about it and they assured me that they would never use
anything but #8 nuts in this application. I called because they still had
the, what seemed like, the original paint primer on them."

 

[stumps]

Many of the older mechanics on this board might remember the great scare that happened across the US with counterfeit high grade nuts and bolts. Some Chinese con men were injecting extremely bad bolts, that were identical copies of very high performance fasteners, into the middle man market. Because these fasteners were made from used oats, they were very competitively priced, and many of the prominent wholesalers were buying these fasteners from undocumented sources, rather than directly from the factories, like they should. These fasteners were showing up in aviation applications, heavy construction equipment, and transportation applications, and stripping, and shearing off like butter.

My dad got some replacement lug bolts from NAPA that turned out to be counterfeit. He installed them in one of his dump trucks, tried to tightened them up to spec, and they would snap off.

Naturally, he was very upset, and went back to the NAPA dealer, and told him what was happening. The NAPA dealer went back into stock, pulled out a bin of studs, and dumped them onto the table. Most made a nice musical "tink" when they bounced off of each other as they dumped out, but about 1/3 went "thunk".

If you looked closely at the bolts that went "thunk", you could tell they were slightly wrong. They were a little too long, and the grade marks were a little rough looking.

I don't recall the exact time frame, but it had to have been in the mid 1980's.

Which by coincidence is when my MF engine was reman'd at Toole.

If you want to learn more about counterfeit fasteners, google "counterfeit bolts".

-Chuck

 

[FMJ]

Chuck there is alot of Guys wanting to get to the bottom of this, me and FMJ especially. I don't plan on tearing the motor down real soon, this breakdown gives me an opportunity to do some refurbishing, painting, seals, tires, and other tasks that are put off during the parade/event season. However, and I've said this in another thrown rod thread, as soon as I tear into it, I'll have some real good photos and a narrative of what I find.

Well, the postmortem on my engine will begin soon with many many pics. . .

 

[USAFSS-ColdWarrior]

Those BUM-BOLTS in the 80's made it into the Foundries and Machinery Industies too.... The company I was working for dispatched CASES of bolts for retrofit to cover our butts. Ultimately, we were COMPLETELY reimbursed for time and labor by our supplier who had provided to us copies of the certifications that had been presented with his bolt orders from his (Chinese?) suppliers. We implimented our own testing and certifation procedures from then on. It was a complicated MESS.... FUBAR, the DELUXE EDITION