Just picked up my first m1078! Air Compressor broke on way home!

Hey everyone! I have some great news. I received my M-1078 this morning from GA. Took a while as the shipper that i had kept flaking on me. New shipper picked it up Friday evening and had it here at midnight last night. Now for the best news. I took the power steering pump and Air compressor off and found that the only thing wrong with it was the Spur gear nut backed off and the gear moved out away and wasn't engaging. I can't believe that's what it was and there was ABSOLUTELY NO DAMAGE! Cleaned it all up and used locktight and impacted the nut back on as it is a tapered shaft. Fired it up and everything runs perfect. I am so **** happy right now. Thank you all for the information in prior posts.

I just saw this. I wished I would have seen it a month and a half ago. We run into this quite regularly on these trucks and I'd have gladly pointed you in that direction. So glad you got it fixed.

Duckworthe said:

... I took the power steering pump and Air compressor off and found that the only thing wrong with it was the Spur gear nut backed off and the gear moved out away and wasn't engaging....

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Can you explain a little more about where the "Spur gear nut" is on the air compressor? Is it visible from just looking at the air compressor installed on the LMTV or do you have to remove it or any guards, accessories?...
Just collecting data on "things to check" and wanted to know if this is an issue that can be seen during a PMCS.

Thanks!
OD

No you cant just see the nut. It is under the front engine cover. You would have to take that off or remove the power steering pump and air compressor from the mount to check it. Sandcobra164 said that this is something he has seen before. However, if your compressor is making air pressure i wouldn't worry about it. My compressor was also gummed up so bad that after i put it back together it still wouldn't make air. I just purchased a new unit and it came with a nylock nut instead of just a regular nut. since i haven't had any troubles.

Thank you Duckworthe for the info. Did your truck have air issues at pickup? I read your original post and it sounded like the pump just gave out on the recovery drive.

Sorry for all the questions but have two more...

The nut you are referring to I am assuming it's part of the belt or pulley assembly that spins the pump?

Which replacement pump did you wind up getting?

Thanks again!

OD

Duckworthe said:

My compressor was also gummed up so bad that after i put it back together it still wouldn't make air. I just purchased a new unit and it came with a nylock nut instead of just a regular nut. since i haven't had any troubles.

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I might be missing something here:

- What difference does that make (regarding performance)?

The nylock nut makes no performance difference besides that it wont back off. My original compressor was a midland the they were bought out by another company (I don't remember the new company name off the top of my head). They send all the new compressors out with the nylock as they know it is a common issue. It was just as cheap to buy reman unit as it was to try and rebuild mine. Also, my truck didn't have an issue at pick up, only after i was 90 miles from the pick up location. HAHA. But that's the fun of it. The nut is located behind the front cover. It holds the gear onto the compressor shaft. Keep in mind that the gear drives the compressor and the power steering pump. The gear/shaft connection is only a tapered shaft so when the nut backs off the gear will only spin on the shaft and nut turn the compressor or the power steering pump leaving you stranded for a bit.

Another note on the nylock nut from the manufacturer. Quote"Use the nylock nut that comes with the new compressor. We have found that even with thread locker and proper torque, the original style nut can still back off." end quote. So i did what they recommended.

Thanks again for the further detail Duckworthe.

I am putting this issue down as a potential item to happen at any time and it sounds like no advanced warning and not detectable at PMCS.

I was doing some reading on a commercial trucking forum this morning where they pointed out that the power steering pump and air compressor are gear driven as you stated (weird coincidence on timing of my research and your reply).

Seems like something that might be a good idea to check during a good at home inspection of all the systems. Maybe while changing the belts. Based on your earlier post, you must remove the front engine cover to get to the nut in question holding the gear on the compressor. My first preventative maintenance reaction would be to swap out that nut with a nylock before any trouble starts.

Good stuff!

OD

good to know information in this one.
might be a good idea to make a pinned post with common problems and solutions or links to the solution.

If the nut is backing off you probably have compressor problems. I'd replace the air governor as a preventative measure.

scottmandu said:

If the nut is backing off you probably have compressor problems. I'd replace the air governor as a preventative measure.

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I agree! The old compressor I replaced was very gummed up with nasty goo. The governor can be picked up from any truck parts place for about $30 bucks. Or you can go to a vender on here and pay $65 if you like.

thread resurrection: I assume that it would be good for preventative maintenance to change out the nut with a nyloc? Do you know what thread size/pitch it would be?

The trucks I've had this issue on are the newer C7 powered variants. It's not an easy task to get to the nut in question. You have to get the front cover off which involves removing everything else in the way to do that. I'd let it ride for now and deal with that issue when it comes. Please let me stress the word "when" as I don't want to paint a picture of Soldiers pulling front covers everyday. Lot's of people are still using Deuces (M35A2's) with hexagonal head connecting rod bolts without issues. If it's not a problem now, there's a rare chance it will be.

I'd have to look, but I seem to recall that there was a maintenance order that was done to replace the nut with a lock nut.

I saw a video of a fellow documenting his recovery who went thru this exact story (in the OP) and even re-tightened the nut when it first came off and the PS/air compressor went down. But it came off again during the trip and resulted in debris which ruined the engine.

That said, I have yet to tear into mine to see if it has or needs the lock nut. But after seeing it cost that guy an engine it's on my "will do" list.

It may be a good thing to put a little loctite on the tapered shaft before reinstalling the gear if they’ve come loose as well

Ryan31783 said:

thread resurrection: I assume that it would be good for preventative maintenance to change out the nut with a nyloc? Do you know what thread size/pitch it would be?

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When you find out, please post it. I would like to get one too.

Third From Texas said:

I'd have to look, but I seem to recall that there was a maintenance order that was done to replace the nut with a lock nut.

I saw a video of a fellow documenting his recovery who went thru this exact story (in the OP) and even re-tightened the nut when it first came off and the PS/air compressor went down. But it came off again during the trip and resulted in debris which ruined the engine.

That said, I have yet to tear into mine to see if it has or needs the lock nut. But after seeing it cost that guy an engine it's on my "will do" list.

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I think this is that video...
https://www.youtube.com/watch?v=a_dBBWOt55E