My new LMTV is blowing water pumps and loosing alternator brackets!

[graniteclimber]

I bought a 1998 Stewart & Stevenson M1078 LMTV from Iron Planet with 13k miles. The truck visually is in excellent condition. All fluids looked new and perfect. Turns out it was too good to be true. Need some help diagnosing this thing.

The truck came from Fairbanks, Alaska. I hired a guy who deals with these trucks quite often to drive it 350 miles to Wasilla, Alaska.

Here is what happened...

1. 36 miles down the road the top bracket holding the alternator vibrated loose and fell off the vehicle while driving. The driver got a ride home (330 miles away) and came back with a replacement bracket off of his personal LMTV. Reinstalled bracket.

2. 4 miles later the truck starts spewing coolant all over the highway. Diagnosed as a cracked water pump.

3. Truck sits on side of the road for about a week, find a mobile CAT mechanic who replaces the water pump with a new unit.

4. Driver goes back to get truck. Re-installs his alternator bracket for the trip.

5. 40 miles later the new water pump blows again. Upon inspection of the engine it is found that the replacement alternator bracket was nearly lost (again). One bolt was gone and the other was loose. I am told they were installed with a torque wrench to the correct spec.

6. Oh F*(#&(*&%# !! %R*#(%#$(*&#% !!!!!!!!!!!!!!

7. Call mobile CAT mechanic. He is pretty surprised and suggests there may be a clogged radiator causing excess pressure or perhaps the head gasket is blown out or starting to fail. Oil still looked new upon visual inspection.

8. Lowboy acquired, LMTV being hauled to Wasilla for further repairs/diagnosis.

Obviously there is a problem with the coolant system and the alternator bracket issue is perplexing. Perhaps something is out of balance on the engine causing the bolts to vibrate loose? I really have no idea.

All this crap is costing me a LOT of money that I would rather not be spending. Any ideas and or suggestions on what the problem(s) may be?

 

[wheelspinner]

I don't have a lot to offer, but get new bolts. I can go into an entire dissertation about over tightening bolts and removing them from their "plastic stage" but if the bolts were ever stretched by over tightening them they will come loose every single time. Think of a spring from a little click pen, you take it apart and tug on the spring; a little further each time, then one time it doesn't spring back. That's what happens to over tightened bolts. The "spring" in the stretch of the bolt is necessary to maintain proper clamping. I'd start by replacing those bolts. Probably more than that, but when it sounds like somebody thought if tight is good, tighter is better, could be a problem.

 

[Bighorn]

The first water pump was cracked.
What happened to the second water pump?
You said it "blew".
How exactly did it fail?

As for clogged radiator or blown head gasket causing a water pump failure, no way.
The radiator cap would relieve the pressure in the system and in any event causing enough pressure to destroy a water pump would split the radiator first.
I agree with Wheelspinner above about the threads of the alternator bracket bolts being stretched and causing them to loosen quickly.

From the information you provided I surmise;
The first water pump cracked either due to freezing of the coolant or manufacture defect or improper installation or damage to the pump housing by other means.
The second water pump failure is unknown without further information as to what exactly was the nature of the "failure".
Did the housing crack?
Did the bearing fail?
Did the seals leak?

I had a friend who was working on a 1974 Jeep.
He went through 4 brake master cylinders in the space of a week.
It was just a matter of poorly re-manufactured master cylinders.
It happens.
Maybe there is another issue at work here but sometimes it is just dumb luck.
Don't be discouraged and just work the problem.
Replace water pump again, check all belts and tensioners.
As for the Alternator bracket; Chase/clean threaded holes, replace old bolts with new bolts, loctite, torque to spec.

 

[Suprman]

I believe this happened to someone else before. There was a thread about it. Kept breaking accessory brackets. I have an alt bracket.

 

[NDT]

I would run the engine with the cab tilted to see why you are getting severe vibration on the engine.

 

[1951M1078]

Crank balancer going bad !

 

[graniteclimber]

I don't have a lot to offer, but get new bolts. I can go into an entire dissertation about over tightening bolts and removing them from their "plastic stage" but if the bolts were ever stretched by over tightening them they will come loose every single time. Think of a spring from a little click pen, you take it apart and tug on the spring; a little further each time, then one time it doesn't spring back. That's what happens to over tightened bolts. The "spring" in the stretch of the bolt is necessary to maintain proper clamping. I'd start by replacing those bolts. Probably more than that, but when it sounds like somebody thought if tight is good, tighter is better, could be a problem.

It is my understanding the bolts were new.

 

[graniteclimber]

I believe this happened to someone else before. There was a thread about it. Kept breaking accessory brackets. I have an alt bracket.

Happen to have a link? I've tried searching for it but not finding anything. Send you a PM about the alternator bracket.

 

[scottmandu]

This could be caused by vibrations coming from worn out driveshafts, or a rough running engine which could be any number of problems.

 

[graniteclimber]

This could be caused by vibrations coming from worn out driveshafts, or a rough running engine which could be any number of problems.

The engine seems to run very smooth, however there are definitely some drive line vibrations when the accelerator is let off

 

[Bighorn]

So the first water pump failed due to a cracked housing.
Then the alternator bracket came loose twice.

What happened to the second water pump?
If the housing of the second pump also cracked it sure sounds like you have bad harmonics in the accessory drive belt.
You ought to be able to observe this if it is violent enough to destroy water pumps and brackets.
Is it possible the wrong belt is installed?
Is the belt loose or flapping?

 

[graniteclimber]

So the first water pump failed due to a cracked housing.
Then the alternator bracket came loose twice.

What happened to the second water pump?
If the housing of the second pump also cracked it sure sounds like you have bad harmonics in the accessory drive belt.
You ought to be able to observe this if it is violent enough to destroy water pumps and brackets.
Is it possible the wrong belt is installed?
Is the belt loose or flapping?

Looks like the seals failed on the second water pump. After the failure I am told the water pump bolts were a bit loose. Tightening them did not slow the flow of coolant.

When the engine is idling with there are not any violent vibrations or anything to indicate the truck is running poorly. Belt is tight and looks correct.

 

[Bighorn]

I would not conflate the cracked water pump housing with the second water pump seals leaking.
The two are unrelated.

Where do you stand right now?
You have the vehicle, it is operable, but the water pump is leaking at the shaft seal.
You also have a vibration upon deceleration.
The alternator bracket has not come loose again.

Is that correct?

One at a time;
Replace the leaking water pump.
Remove and inspect the rear driveshaft and pinion and transfer case yokes. OR;
Okay, you can block the wheels, release the parking brake, put the transmission in neutral, climb under the vehicle and grab the rear driveshaft and push up and down.
Twist it.
Try to find any peculiar play or looseness.

Check the torque of those alternator bracket bolts again to see if anything has come loose.

You have a few separate issues.
A driveline vibration upon decel has nothing to do with loosing water pumps.
The alternator bracket could possibly have some connection to your water pump issues since they are related by the drive belt.

Start with replacing the water pump.
Check the alternator bracket.

Then check the driveline.

 

[Bighorn]

Looks like the seals failed on the second water pump. After the failure I am told the water pump bolts were a bit loose. Tightening them did not slow the flow of coolant.

When the engine is idling with there are not any violent vibrations or anything to indicate the truck is running poorly. Belt is tight and looks correct.

Ahh. I missed that first part.
So your water pump leak wasn't even from the shaft; it was fron the gasket due to loose mounting bolts?

Dude, I am sorry.
You said a "Cat mechanic" replaced the water pump after the housing cracked.
You need a new mechanic.

There is perhaps an argument for a few "stretched bolts" allowing the alternator bracket to come loose.
But a water pump being loose so soon after installation is unforgivable.

Just start over from the basics.
The thing needs a new water pump gasket.
Is that correct?

 

[Awesomeness]

This is the exact same story that has happened to me. I cracked the water pump housing, then vibrated all the bolts out of it, broke the alternator off, broke the starter off, cracked the engine block, replaced the engine, broke alternator bracket bolts, and cracked a transmission line. After I broke that L-shaped alternator bracket (same as you) the first time, I made a new one out of 3/8" thick steel angle, so the second time around it broke all the bolts off and flopped around beating the snot out of everything.

Unfortunately, since I've replaced the engine and still broke a few new things, I don't think the problem is gone yet. However, at least I've spent $7000 to narrow down that it's not the engine itself, haha! Next thing I'm thinking to try is balancing the driveshafts, mostly just because they are low hanging fruit.

 

[coachgeo]

This is the exact same story that has happened to me. I cracked ...Unfortunately, since I've replaced the engine and still broke a few new things, I don't think the problem is gone yet. However, at least I've spent $7000 to narrow down that it's not the engine itself, haha! Next thing I'm thinking to try is balancing the driveshafts, mostly just because they are low hanging fruit.

If you can find a body shop that does work on commercial trucks... maybe they have the means to verify your chassis is straight. If it is tweaked it would explain a lot of what is happening.

 

[Awesomeness]

If you can find a body shop that does work on commercial trucks... maybe they have the means to verify your chassis is straight. If it is tweaked it would explain a lot of what is happening.

It's worth a shot, but I doubt that's it. My LMTV is pretty pristine, almost amazingly so. No dents, no dings, nothing looks broken or replaced, etc. Then Pvt. Murphy comes a knockin', and everything that moves or turns needs to be destroyed. At this point it's getting super annoying, as I just want the **** thing to drive 20-30 miles without wrecking crap and stranding me.

It's pretty crazy how much my story starts exactly like the original poster here. I replaced the cracked water pump housing. Then it vibrated all the bolts out of the water pump housing after I had put it back together well. Then I broke that same exact L-shaped alternator.

 

[tennmogger]

Would it be reasonable for us other LMTV drivers to ask how you drive your truck? Are your trucks part of the group who have top speeds at 56-57 mph, that is, driven foot to the floor on long drives? That may not be an answer that comes easy.

For every accessory that hangs on the engine block to have broken loose, the engine must have had tremendous vibration. That has to be noticeable, and should call for investigation before catastrophic failure. Sitting right on top of the engine, every noise can be heard, or actually felt.

No doubt we all want to understand what is going on!

 

[Awesomeness]

It broke all that stuff while keeping it in the 50-55MPH range, below totally floored, though it does happen when driving at higher constant speeds (for <20 miles). And no, it's not noticeable in the cab, at least through all the noise and vibration the truck generally generates.

 

[tennmogger]

Thanks for the feedback! Your comment that the truck has "all that noise and vibration" may be a further clue that you do have some underlying issue unique to your truck (considering your results, my comment is "well duh"!). Other than a little drive-line chatter occasionally, mine is not particularly noisy.

Is there an opportunity for you to ride in another FMTV for comparison?

Awesomeness, where did your engine block break?