M928A1....to scrap or not to scrap...that is the question.

[Ferroequinologist]

I have a known good set of injectors we can put i n to see if that's your problem.

 

[wreckerman893]

Let me inject (no pun intended) this into the mix. If water makes it past a filter and goes through the pump and is sent to the injectors it can turn to steam and pop the tip off an injector. This allows raw fuel to enter the cylinder in a stream and hit the piston. If this happens the raw fuel can burn a hole in the piston and cause the noise you describe. Did the truck seem to be pulling real good right before the knocking started? This happened to me many years ago when I was running west coast. I was driving someone else's truck and unbeknownst to me (and the Boss) he had turned the fuel way up on the 400 Cummins in the truck. I melted a hole in the piston because I kept my foot in the fuel while pulling a heavy load up a long gradual hill in CA. I was lucky enough to limp into the parking lot of a shop before I shut the engine down. The mechanic told me what had happened and showed me the holy piston. This is another reason you have to be careful when turning the fuel to an engine.

 

[mcshooter79]

The knock was there when I picked up the truck so I don't know what it was like before it happened. The repairs I will need to make are to whatever let go inside the motor. I need to pull the pan and see what it looks like inside and fix the rod, or piston, or spun bearing, or whatever it was that broke inside the block before I'm worried about the injectors.

Remember it was knocking but running fine otherwise and then it started making allot of "clatter" whenever I took the load off and the engine was decelerating. And then while listening to it at idle something "broke". I mean the engine shook a little and it started making ALLOT of racket like something being bounced around inside the block and you could feel that something was hitting something .

So what I mean is first I have to decide if whatever the major damage is is fixable before I dig into the fuel system, which maybe the root cause of the problem.

The scenario that Wreckerman893 is describing is kind of what I'm wondering may have been the issue with my truck. It would seem to explain some of the initial symptoms I think.

 

[CBR Metalworks]

Did yours have oil in it when you picked it up? Mine was bone dry on oil and transmission fluid.

 

[mcshooter79]

Engine oil was good but tranny needed almost 2 gallons.

 

[mcshooter79]

I have a known good set of injectors we can put i n to see if that's your problem.

Thanks for the offer, It will be a little while before I'm at that point, but thank you sincerely.

 

[CBR Metalworks]

did you ever get the truck home?

 

[mcshooter79]

I remember that set up. Wondering how the rear overhang will work out.

I used the same carrier that I used to get my two 931s home and after doing some improvements and reinforcement it worked like a charm. The guys at the lot where the truck had been sitting were super nice and they just lifted the front end of the M928 with one of there wreckers and I backed underneath and they set it down in my carrier. Once I pulled the rearmost drive shaft just for peace of mind it towed as nice and stable as I could ask for, I'm pretty sure it would have been stable up to whatever speed I wanted to go. One thought on my carrier vs a lowboy trailer is with my carrier I probably do have quite a bit of aerodynamic drag with the cab sitting up as high as it does that I wouldn't have if I had the towed truck on a lowboy. The top of the M928 cab was about 12' 6" high.

The rear overhang dragging the ground can be compensated by suspending the fwd rear axle as high as possible. Note avatar, I have some experience!

Recovery,
I had to do just that. As you can see from the pictures the pintle on the M928 is less than a foot off of the ground, although except for pulling into the gas station where these pictures were taken, it never touched or scraped throughout the tow home. Before I chained the middle axle up to the frame the tow pintle was just kissing the ground.

did you ever get the truck home?

I did get it home just 3 days ago but I still haven't looked inside the motor yet.


I'm hoping to be able to pull the oil pan on the M928 in 2 weeks. Unfortunately I have to leave the truck at the family farm just north of Gainesville FL and I live in St Petersburg so it's a matter of when I can get back up there. I will be sure to post an update when I get inside and see what happened.

 

[mcshooter79]

OK so I finally got a chance to look inside but the results are not exciting. There is nothing wrong that I can see. There was no obvious metal in the oil and no giblets in the oil pan. There wasn't even much metal on the drain pug magnet as compared to others I've seen. A bunch of intact connecting rods attached to complete pistons. All caps in place and nothing out of the ordinary. I guess I haven't eliminated the possibility of a spun bearing but I didn't see anything obviously wrong like I thought I would. There is definitely some interference some where because you can just feel it when the engine was running for those few seconds after the mystery failure. You can feel something is hitting something, the impact can be felt and seen when looking at the engine. My next thought is maybe the air compressor came apart???? There was some coolant that came out when I drained the air tanks so I already figured that I had a bad head gasket but I didn't have time to repair it before I needed to get on the road so I ran it as is. I think I may have noticed that the compressor seemed to take longer to build pressure as I was driving it so...........maybe there was a catastrophic failure of the compressor? There is no evidence of damage on the outside of the compressor however. I wish I had the truck at my house so I could dig into it further but right now this is where I am. Any other theories??

When whatever failed...failed... It still sounded like the engine was firing on all 6 which was baffling to me at the time?? Another note, I had good oil pressure the entire time, although maybe too high. On the gauge in the cab the pressure never dropped below 60 PSI that I remember and I want to say it was as high as 80 when idling cold...does that sound right?

I'm afraid the pictures are a little boring since there is no broken stuff to look at.

 

[Tin Medic]

I'd say that the fact there are no random pieces laying in the pan is a good sign. I hope you get it back up and running and can drive it home.

 

[mcshooter79]

Anybody else have any ideas on this? Could it be the air compressor?

 

[bigboy44]

Just a FYI I put a mechanical oil pressure on my 250 and cold it ran 85 psi. Good Luck, that is too nice of a truck to scrap.

 

[wrenchturner6238]

If you had some antifreeze in your air tank (if i remember right you said you had some) it very well could be the air compressor. It is going to be a little difficult to check but first off i would top off cooling sys PSI up the cooling system take the PSI up at least to cap PSI (not much over you could make coolant leaks) remove the air compressor discharge line and let it set over night with PSI and see if you get some antifreeze out of the fitting. Other checks to the compressor will involve some work like taking it off and check how it turns. Most air compressors have a cover to gain access the connecting rod take it off and inspect like you did with engine.

 

[mcshooter79]

Well I know that it has been awhile but I finally got a chance to work on the truck again and I figured that I would post an update. With the other issues that I had with the truck long the suspect compressor and the minor knocking I assumed that whatever had let go would be related but it looks as if it is not. So I pulled the compressor off, which has some bolts on the back side that are a real PITA to get loose, and it was actually fine. So then I did something that I wish that I had thought to do before. I had my father bump the starter while I was under the truck and feeling around and I discovered that the major knock was coming from the rear of the motor, in fact it was coming from the bellhousing. I pulled the inspection plate off of the passenger side of the bellhousing and the front of the flywheel has obvious nicks and dings where it has been hitting something. I noticed in the TM it talks about the possibility of dropping bolts for the torque converter in there and that they would cause and obstruction so now I almost wonder it one of those backed out and is now in there jamming up the flywheel. I guess my next move will be to pull the transmission and see what I find but who knows, that may be another year or two down the road.

On a related note, for those of you that have pulled transmissions from these was it easier to pull the whole motor and trans as an assembly out of the front (I have a wrecker for the lifting) or drop the transmission by itself out the bottom? I saw a picture where someone was using a chain hoist through the access panel in the cab to drop one. Any special problems or things to look out for when pulling these motors/transmissions? Thanks in advance.

 

[simp5782]

Well I know that it has been awhile but I finally got a chance to work on the truck again and I figured that I would post an update. With the other issues that I had with the truck long the suspect compressor and the minor knocking I assumed that whatever had let go would be related but it looks as if it is not. So I pulled the compressor off, which has some bolts on the back side that are a real PITA to get loose, and it was actually fine. So then I did something that I wish that I had thought to do before. I had my father bump the starter while I was under the truck and feeling around and I discovered that the major knock was coming from the rear of the motor, in fact it was coming from the bellhousing. I pulled the inspection plate off of the passenger side of the bellhousing and the front of the flywheel has obvious nicks and dings where it has been hitting something. I noticed in the TM it talks about the possibility of dropping bolts for the torque converter in there and that they would cause and obstruction so now I almost wonder it one of those backed out and is now in there jamming up the flywheel. I guess my next move will be to pull the transmission and see what I find but who knows, that may be another year or two down the road.

On a related note, for those of you that have pulled transmissions from these was it easier to pull the whole motor and trans as an assembly out of the front (I have a wrecker for the lifting) or drop the transmission by itself out the bottom? I saw a picture where someone was using a chain hoist through the access panel in the cab to drop one. Any special problems or things to look out for when pulling these motors/transmissions? Thanks in advance.

It takes just as long to pull them together as a motor trans combo than just the trans itself. Also makes em putting it back together easier

Sent from my SM-G860P using Tapatalk

 

[Tracer]

I think your getting close. Be patient and don't scrap the truck.

 

[Coffey1]

Here's what I would do if you suspect a bolt.
You don't have to remove entire transmission build a carriage under tranny with pipe rollers or wheels and separate the transmission just far enough to let bolt fall out.
Hopefully you got some concrete to work off of if not a 3/4 sheet of plywood leveled out will work.

 

[spectra3279]

Pull injectors and rotate flywheel with a prybar. Look for missing bolts on the torque converter. You may also be able to get the bolt to fall out. If not use an inspection camera to look around.

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[71DeuceAK]

Definitely, definitely, definitely, DO NOT scrap it. 928's are pretty darn rare, there were only about 500 of the 927/928 ever made as I understand it and many have been chopped up into other things. IF you decide you're scrapping, I'm on the hunt for a 928. Running or non-running. Would possibly give you slightly more than what you'd get for it in scrap to make it worth your while but it might take a bit of time for me to get it out of there. PM me if you decide to go that route, and in the meantime good luck!

 

[74M35A2]

The flywheel housing should have a removable access cover of how the torque converter bolts are installed. Remove it and rotate the engine to check if all present. Mark the first with marker or paint.

I'd sell the truck to somebody here if everybody loves it that much.