LMTV Alternator Disaster, engine now catastophic

[Awesomeness]

With our setup you separate the batteries. Say two 12 volt connected parellel for the 12 volt and say two 12 volt batts connected in series for the 24 volt side.

I don't understand how that's an advantage. The batteries aren't doing much while the engine is running, so they are mostly for starting the truck. So with your system you are using 1/2 as many batteries to start the truck?

As for the picture of the burned alternator, that's the first I've heard of one catching fire. I don't doubt it happens, but I'm pretty sure you could find a picture of an edge-case of every electrical component in the truck that has caught fire at some point. In my years here on SS, I don't think I've read one story of an FMTV alternator catching fire.

 

[aleigh]

So both a diesel truck mechanic and an ex-mil helicopter mechanic have opined about this situation that the plastic fans are not rated for a 100% duty cycle (and my fan clutch was stuck on). They are thinking brittle old plastic, micro fractures, design strength, etc. I notice a lot of the 3116 applications are metal fans w/ the viscous couplers you find in ordinary cars instead of the selectable air clutch arrangement.

 

[aleigh]

For everyone who asked about the schematics, look in TM 9-2320-365-34-2 at the end and go up a few pages.

 

[Adventure Driven]

I think it would be good to find a viscous fan clutch with metal fan blades, I would be down to convert mine, one less thing to worry about.

Seth

So both a diesel truck mechanic and an ex-mil helicopter mechanic have opined about this situation that the plastic fans are not rated for a 100% duty cycle (and my fan clutch was stuck on). They are thinking brittle old plastic, micro fractures, design strength, etc. I notice a lot of the 3116 applications are metal fans w/ the viscous couplers you find in ordinary cars instead of the selectable air clutch arrangement.

 

[Awesomeness]

So both a diesel truck mechanic and an ex-mil helicopter mechanic have opined about this situation that the plastic fans are not rated for a 100% duty cycle (and my fan clutch was stuck on). They are thinking brittle old plastic, micro fractures, design strength, etc. I notice a lot of the 3116 applications are metal fans w/ the viscous couplers you find in ordinary cars instead of the selectable air clutch arrangement.

My fan clutch was stuck in the on position for many years before I owned it (judging by the corrosion on the incorrectly installed fan clutch switch that wouldn't have let it turn off even if the clutch wasn't stuck), plus the years I owned it.

A fan blade can't have a duty cycle. It is either strong enough to survive the vibration of being engaged, or it isn't (yes, resonance builds up, but if it can survive being on for more than a hour, it's essentially going to survive forever). The plastic could experience fatigue, but metals are actually more susceptible to material fatigue than plastics are. This is so unlikely that a more realistic explanation would be that the age of the rubber or plastic degraded enough to fail.

The metal fans are far less efficient air movers. My guess is that the ridiculous cooling system specs that are needed to meet for these trucks demands the high CFM plastic fan. The ability to manually shut the fan off for fording water demands the clutch style used.

 

[aleigh]

My fan clutch was stuck in the on position for many years before I owned it (judging by the corrosion on the incorrectly installed fan clutch switch that wouldn't have let it turn off even if the clutch wasn't stuck), plus the years I owned it.

A fan blade can't have a duty cycle. It is either strong enough to survive the vibration of being engaged, or it isn't (yes, resonance builds up, but if it can survive being on for more than a minute, it's essentially going to survive forever). The plastic could experience fatigue, but metals are actually more susceptible to material fatigue than plastics are. This is so unlikely that a more realistic explanation would be that the age of the rubber or plastic degraded enough to fail.

The metal fans are far less efficient air movers. My guess is that the ridiculous cooling system specs that are needed to meet for these trucks demands the high CFM plastic fan. The ability to manually shut the fan off for fording water demands the clutch style used.

I am unconvinced this is the problem (just like I am unconvinced it's driveshaft vibration when none of my bolts save one were loose) but I am also unconvinced by the naked statement "a fan blade can't have a duty cycle". Of course it can. I think perhaps you meant to say "fans lifespan under design conditions is the same regardless of duty cycle" for which I retain a healthy skepticism. Like you conclude though and I have said already a few times on this thread, I wonder about the age of the plastic. Certainly everything else plastic and rubber seems to fall apart on these trucks, and other milsurp gear.

 

[Awesomeness]

A duty cycle is an amount of time the device can be in operation, in relation to a necessary period of rest before it can become capable of performing the cycle again. Most commonly that is related to heating of electrical components. There's nothing about the fan that needs downtime... it either survives or it doesn't. At work, even our most torturous vibration tests of critical manned spaceflight components are just a couple hours long. If it survives the couple hours, we're betting people's lives it will survive a very very long time in that environment (essentially indefinitely, barring some other effect on the material, such as UV degradation, thermal cycling, etc.). A fan can not have a duty cycle.

Also, the cooling system is designed to fail with the fan on. In hot environments when hauling, the fan runs basically all the time. So your instance of the fan running constantly doesn't really represent an unusual case that should have created an unexpected failure. Keep in mind there are 100,000 of these trucks out there, and millions of other vehicles with plastic fans of various ages. If you're going to stick with the "plastic fans suck" theory, the more difficult part is explaining why millions of other ones work just fine.

I am unconvinced it's driveshaft vibration when none of my bolts save one were loose

I know you're unconvinced, and ultimately it's playing odds so there is a small but present chance you are correct. You could have had failures of several "unrelated" components (fan, alternator bracket, water pump, u-joint) in a close amount of time, and they were each just individual components reaching their lifespan. "Truth is stranger than fiction", and all that, there are going to be edge-case stories like this about everything we could imagine. My point is that if they are all related to a single root cause driveline vibration, you have a high risk of fixing these symptoms, only to experience them again, or worse. When it happened to me, I think I just wanted to believe they were unrelated, even though I had thought logically they probably were connected.

You said you were likely to get the driveshafts balanced anyway, so I guess you'll know more once they tell you what condition they are in. If they are in good shape, you'll be vindicated. If they aren't, you'll have some new things to consider.

Which one bolt was loose? Bolt in what component?

 

[frank8003]

I so suck at TM's, someone make a u tube video on how to use the darn things LOL Seth

I quote from the following short read ..........
Military manuals are a great resource, one which people, even people in the military, don’t generally appreciate. The common complaints include they are hard to read, boring, poorly written, etc.. But as they are not great literature and they were not intended to be, they are working instructions and notes.
They are loaded with a vast amount of information, accumulated with great difficultly, often at the cost of many peoples lives. A lot of effort, a vast amount of experience, time and thinking, not to mention money, went into making them."

here is the rest of it at http://www.military-info.com/freebies/value.htm

That said there is a few time saving tips and tricks available for the asking but first say what it is you want.

 

[porkysplace]

I so suck at TM's, someone make a u tube video on how to use the darn things LOL

Seth

Right there in red is the problem , it's getting where expect a youtube video to solve their problem . They don't want actually read anything to learn the answer and that is what it takes to use TM's . Depending on what your looking for you may need to read a chapter (or section depending on how the index is laid out) or two , you may have to read it twice to understand it . It is the same with searching threads here on SS , most of the time you need to read the whole thread to find the answer . I prefer paper manuals for 2 reasons 1. that is all there was when I learned to turn wrenchs 2. What are you going to do when your in the middle of nowhere with no cell phone service or internet , your not looking on youtube or SS for quick answer for a quick fix then. Even if you have the TM's downloaded on a device batteries go dead and they crash for no apparent reason at the worst possible time.

So you want to learn to use a TM , here is a TM on how to use a TM ( just got to love our military )
[h=1]How to use/read Technical Manuals[/h]And this is How to find a part in the TM's.
[h=1]How to find a part (educational--I hope)[/h]

 

[Suprman]

The clutch will fail before the fan does. The only damaged fans I have seen are after the clutch came apart and the fan flew away.

 

[frank8003]

I so suck at TM's, someone make a u tube video on how to use the darn things LOL Seth

OK, here is a youtube for you. Will Eisner originals are the PS magazine.
You will have to read the PS magazines to find if your problem has been addressed.
Here is your youtube
https://www.youtube.com/watch?v=jZQreoQ3CNM

 

[frank8003]

~ So you want to learn to use a TM , here is a TM on how to use a TM ( just got to love our military )~QUOTE]
porkysplace big attaboy here

As in everything things change. Remember that a TM is one of the few things you can read that has NO advertisements, and TM's get thrown away when the equipment does.

About changes, and what is here and been on the way since 1979 [and that is pre-puter era] is a problem associated with ninth grade.

So,I found a way to post this directive as some wouldn't click on it if was just a link, or could just watch a video. One must read it.

 

[frank8003]

This is from overdrive, 10232015

Army PS Magazine Index of all FMTV Articles with Subject, Issue, and Page Numbers

https://www.steelsoldiers.com/showt...-Articles-with-Subject-Issue-and-Page-Numbers

10-23-2015, 11:53 from overdrive

 

[aleigh]

Which one bolt was loose? Bolt in what component?

At the risk of sounding rude, did you actually... read my thread? This has all been covered in great detail. It has been recounted here several times already but here is what I think most likely, and what every professional mechanic who worked on the truck so far thinks:

1. The bolt works loose over a long span of time due to free play because the alternator mounting holes were rounded out. I fail to detect this and fail to tighten the bolt. Once it works out, the alternator has significantly more free play and is "hanging" off the two upper mounting bolts.

2. Alt snaps off the bolts and falls off the engine shortly thereafter. This drops the cooling belt coincidentally.

3. Engine overheats and blows steam out through the water pump damaging the o-rings.

4. Shortly thereafter the water pump fails to hold water.

Think whatever you want about the fan. The engine previously threw a blade prior to my owning the truck, and as soon as another fan gets put on it, it throws a blade. Someone could look at that and say it was just balancing itself. Someone could look at that and say the fans that have been sitting around in a warehouse for decades are compromised. Someone could say it was just a manufacturing problem.

 

[Awesomeness]

Yeah, I read the thread in detail. I asked because you previously mentioned a number of bolts missing or broken, but none that you found loose, and then you were just mentioning the loose one now after talking about the driveline, so I wasn't sure if you were talking about one of the u-joint caps or something else.

That long alternator bolt (which is what I think we're talking about now, since you still didn't actually say it specifically, you just say "the bolt" and "the bolts") is supposed to have a locking nut on it. Whether or not it had one on it before, make sure to use one now, probably with blue Loctite too.

The time I broke the top L-bracket on my alternator, the long bolt remained in place, but had "loosened". The vibration of the alternator had beat the large "roll pin" / slotted bushing in the rear bottom ear of the alternator into the casting of the curved alternator bracket, leaving a dished divot. That was during about a 30 mile drive. Once it has some wiggle room, it definitely is able to cause a lot of destruction. I ended up having to machine that divot off to create a flat face again, then take up the gap space with hardened washers.

 

[aleigh]

"Snapped the two bolts going into the engine and the big long bolt is nowhere to be seen."

By which I mean the two going through the L bracket into the engine snapped.

 

[Awesomeness]

Did your L-bracket damage the top of the the curved cast alternator bracket? Mine did, and I had to have that surface machined flat again, and put in a steel shim spacer to make up for the missing metal. You want to make sure everything is flat, mating, and tight, when it goes back together. Any wiggle room and it might break again.

 

[Suprman]

I have an extra stock alt bracket. The big curved one.

 

[DOUBLE ALT]

I was only talking about the lower long bolt on the Niehoff alternator. It is the wrong diameter. It needs to be 1/2 inch .500"
The very heavy alternator loosens the bottom bolt and the movement then loosens, breaks the top smaller bolt. Very poor design. Alternator top bracket bent with too small a radius. No doubt it is cracked before the paint goes on it.
I have seen several broke in the same area. All the vehicles alternator bracket need to be looked at. The bracket needs to be removed and welded on to beef it up. A larger bolt would help. Our alternator uses a 1/2 inch bolt top and bottom. Lock washer or Loctite makes no difference.
You can see the heavier top 1/2 inch bolt in the picture.
Double Alt.

 

[Suprman]

The double alt will be a hard sell to most lmtv owners since it requires reconfig of the batts. This will get alot more complicated on A1 trucks with the advanced charging components.