Cracked! Something else to check on your FMTV...

[Pointman0853]

After returning from OE18, I gave the beast a through wash down. On a short trip to the local dump, I noticed a small oil leak that was found to be loose flange fittings on the small oil 'pipe' between the head and the fuel governor.

Closer inspection revealed this...



a cracked front gear case! I have read about this happening, sometimes as a result of sustained high speed running. Closer inspection revealed that it has not traveled to the front edge or inside rear edge of the case.



I have a welder coming by to have a look to see if it can be repaired I place. I dread the thought of pulling the front of the engine off, so we will see. Here is another reason to run the higher speed gears and slow the little kitty motor down..

After starting the process of removing the power steering pump and compressor, for better access, I found that the single 8 mm bolt that holds the back of the compressor to the support bracket was finger tight.
My fix for this will be to use a longer bolt and back it up with a nylock nut on the back.

I pray this is a short post and will update with pics as the repair progresses.

Check your own support bracket bolts and post up what you find!

Pointman

 

[Awesomeness]

After starting the process of removing the power steering pump and compressor, for better access, I found that the single 8 mm bolt that holds the back of the compressor to the support bracket was finger tight.
...
Check your own support bracket bolts and post up what you find!

Loose air compressor brackets cracking this front housing is a known issue, reported in several posts. It's in my troubleshooting guide here in my signature. I really hate seeing people break the same "known" things over and over... that's why I have been compiling it. If you haven't read it, it's probably a good time to give it a look.

[h=1]Loose air compressor bracket[/h]Check the air compressor bolts on the front housing and look for the bracket that holds the air compressor and power steering pump up from the rear (that’s not attached to the front housing). Loose bolts here cause the front housing to crack from supporting all the weight of the air compressor and power steering pump combo, and is quite an ordeal to fix. Another suggestion is to remove the front plate, not totally but just enough to get to the nut on air compressor, and change to a nylon lock nut. The OEM nut will back off letting the gear come forward and you will lose air and power steering. There's no keyway on shaft, it's just tapered.

There is a rear support bracket on the back of the air compressor that sometimes comes loose, and the vibration can break the hard oil line nearby (see image below). If that oil line breaks, you’ll pump all the oil out of the engine and destroy it. - Suprman

 

[pontiac62]

I read your past post about replacing your front driveshaft with nos. Did your rear driveshaft didn’t have any play in it?


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Man of few words

M1081 LVAD

 

[Pointman0853]

Yes, I had both front and rear driveshafts rebuilt and re-balanced. Now looking forward to installing my 3.07 gears.

Darn house remodel has gotten in the way of any forward movement on the 1078...

Pointman

 

[Pointman0853]

Awsomeness,

Yes, well there is no one more sorry than me that I did not read those posts before setting off on our latest 'trek' to OE18'...
Lets be clear, 'I' did not break it. These trucks are perfectly capable of self-breaking. I could have caught this but didn't, so my bad.

I did get the compressor and power steering pump off this morning. My 'assistant' was a racheting cargo strap to keep the whole contraption from dropping while the the bolts came out.

That's a big nut on the end of the compressor. Loctite Red, or nylock nut?

Still waiting for my local aluminum welding expert to come over... the crack is only about an inch in length and easily accessible.

Pointman

 

[Awesomeness]

Yeah, I know "you" didn't break it. I check mine every time I'm wreching on the engine, just to make sure it hasn't moved.

You can use Loctite Red, if you degrease the threads on both parts well. Some people have recommended the nyloc nut, but I would want to see if the thread engagement of the nut is the same and some threads still made it through the the nyloc portion (usually a nyloc nut is deeper than a regular nut because of the nyloc ring, or the nut engagement is less to make room for the nyloc ring in a nut of the same height).

 

[Duckworthe]

My new compressor came with a nylock nut from the factory and the paperwork said to use it and not the original nut.

 

[Awesomeness]

My new compressor came with a nylock nut from the factory and the paperwork said to use it and not the original nut.

And it looks like a standard depth nyloc nut?

 

[Duckworthe]

It did. But I switched it 2 years ago so my memory is foggy on it. What I do know it the original nut cam loose but was still held on the end of the shaft because the cover is close to the end of the shaft. I know threads came through the nylon.

 

[Pointman0853]

I puled the nut off of my compressor today and meticulously cleaned it and the shaft with acetone before reassembling it with Red Loc-Tite.

A couple of shots with the air impact and I feel good about the prospects of it staying put.

Should have the beast back one the road this week.

Next, install the 3.07's

Pointman

 

[Smike740]

Were you able to repair the crack by welding? Glad to hear you will be back on the road soon!

 

[Ornduff]

Thank you to you guys I checked my truck today and the bracket was missing all 3 bolts from the block side of it. And it looks like I might have a hairline crack. At least I caught it now I guess.

 

[Pointman0853]

I just printed out all the TM's required to do the repair and it is daunting to say the least.

I wonder if anyone has direct experience in replacing the gear case with the engine in the truck, feel free to chime in. Pulling the cam gear while leaving the cam in place would be a huge plus. TM says you need to heat it to 600 deg to put it back on...

Pointman

 

[Smike740]

I have done the repair however I pulled the cam. Unfortunately to pull the cam you also have to pull the radiator. Thle repair wasn’t difficult but did take some time since a lot needs to be removed.

 

[Pointman0853]

Smike740,

Thanks for replying.

The cam gear appears to be a press on arrangement. I may try and use a gear puller and heat to remove it to avoid without pulling the radiator, and all the valve gear. I do not have the special tools required to reset the fuel timing and that is scary just reading it.

I have had two expert tig welders in my area tell me it cannot be welded in place as the block acts as a heat-sink, and the work-piece cannot attain enough heat for an effective weld. Additionally, welding a crack with oil in it can cause the crack to burst on the back side and contaminate the engine.

One expert told me to grind the crack into a 'V' shape with a die grinder, and fill with J B Weld. Since I have nothing to lose, I may try this. I would create the 'v', then bolt on the compressor and support bracket, and finally fill the crack.

I do need a temporary fix so i can move the beast and facilitate the pumpkin change I had planned.

Mr Murphy will not prevail!!!

Pointman

 

[Smike740]

I believe pulling the cam gear with a puller is possible, however you still may need to pull the cam forward a small amount to get enough clearance to get the puller arms behind the gear.

Regarding fuel timing etc. You don’t need to worry about synchronizing the injectors and likely the effect to the fuel setting would be minimal with just removing the governor.

You would need to reset the valve and injector rocker arm clearance if you take the rocker arms off. Fortunately you only need a wrench and feeler gauges to reset the clearance.

JB weld would probably work short term if the compressor support bracket is tight.

When mine was cracked I was able to buy a used front housing for less than $200 from a truck salvage yard, if I remember the part new was close to $1000.

If you have any questions let me know, even synchronizing the rack etc is not as bad as it sounds in the TM.

 

[Pointman0853]

We have an active National Guard facility in Carson City that has 30+ trucks, and most are LMTV's. I'm thinking of going on the community forum and doing an advert for 'Help Wanted-3116 project' and see if I can snag a mechanic, if it gets to that point...

Pointman