Engine problems

[jfnemt1ff1]

There is no question that these engines make diffrent noises. As how you drove it, I have done worse and still runs the same. When I bought mine it had a diffrent type of knock that came in at 2000-2300 rpm. Have drove the truck all over an long trips towing my M725, And my Goat. The noise never changes. When I changed the oil before the trip from Michigan to Iowa I changed all the fuilds and run the oil from the filters after ripping apart through white paper and found no metal. The truck towed the Gama Goat along with about 5000lbs in the bed with out any problems. The help you have got here so far is great. Again a HUGE well of info if you have the tools to check the outside of each cyl and you might find one lowwer.(fuel problem). But like others said try to find the noise before you take apart. I used to rebuild alot of gas engines and it is always better to do that first. And like you said its not to hard to take the pan off to check the bearings.
John

 

[FreightTrain]

I run all mine way up there in the RPM range and run them HOT on the pyro.No Failures yet from it.All my failures have been return line blew twice,Turbo let go(was sloppy when I put it on should have known better),Broke some rings when I let it sit for a full axle seal and bearing replacement(rings rusted to the Cylinder over 4 years).I run gasoline,Diesel,Motor oil(well,the junk from the motor oil tank at the parts store),all straight and in a mixture of all ratios.Run at 2800RPM for hours at a time when I am going to rallies or events.Run 1300(hit 1500 one time for about 2 seconds) on the pyro on hills and accellerating and stick around 1000-1100 steady driving down the road.So.....yea,they can take a beating.I have NEVER been left stranded by ANY of my trucks.I fixed the fuel lines with parts at work cause they exploded in the parking lot.The turbo blew on the way to work a month earlier and I drove to the race car shop 2 miles away from the Failure spot.Blowing a 1980s style skeeter sprayer truck fog bank the whole way(Anyone remember those old things.Loose sight of entire BLOCKS when they came though?).

 

[randyscycle]

Judging from the oil pressure reading you have at idle (30PSI) I'd say its a safe bet there isn't a connecting rod or main bearing issue, otherwise that oil pressure would drop to nothing at idle.

If anything mechanical, I'd say maybe a wrist pin, because they can knock and not affect the oil pressure reading.

I'd definitely do the injector thing, and listen around really carefully first, but I don't think you're dealing with a bearing issue.

If it does in fact turn out to be a bearing issue though, don't just install a new set of bearings on an old crank even if it looks OK. Many times once a bearing does fail, the hammering of the rod forcing down onto the throw of the crankshaft without the oil cushion will tend to beat it out of round, and new bearings will just do the same thing in short order.

 

[DDoyle]

The air compressor suggestion earlier is a great one, and fairly easy to check (especially if you have the special compressor wrench, but it is not impossible to check without it) Pull the compressor belt and see if the knocking goes away - if it does, then obviously you've found it.

I still lean toward it being a fuel injection issue. If, using a stethiscope, you can isolate the loud cylinder, trying swapping injectors with one a couple of holes away and see if the knock moves with the injector.

Regards,
David

 

[m16ty]

Information update on the Hercules installed by Uncle Sam
I looked at the right rear side of the block above the starter.
There are three rows of information.
Starting at the top: FSCM28265
2nd row; 11610199
3rd row; a design with oblong circle with a "M" in it with a small "c" below the M inside the oblong circle. Next is a large 46 and then in the cast tag is "KO18" just forward of the 46.

The data plate very clearly says " date of manufacture 4-91" and the serial number is 3999517.
There are no rebuild tags installed nor are there the holes for the rebuild tags to have ever been installed.
I agree that the "date of manufacture" is not correct and is should be "date of rebuild" or "date of re-manufacture" but it is odd that it does not have the additional rebuild tag as required by Depot Overhaul so that the next mechanic knows what size bearings and bore are now incorported.
Jim

If it says 4-91 on the data plate that has the brand of enging at the top of the plate it very well could have been made in '91. The info I have says the last engines were in '88 but who knows. I've never seen a manufacturers data plate changed out on a engine for a rebuild. I've just seen a rebuild tag added.

I may be over my head on all of this though. Maybe David will chime in.

 

[FreightTrain]

I think mine also says Manufactured in 91.I will see about getting a picture.

 

[FreightTrain]

My bad,Was date of Manufacture 5-90 by Herc.

 

[jasonjc]

I have one with a '90 or '91 build date too. The truck I drive the most, I ran it out of oil one time. Did an oil change every thing looked good took it to lunch shut it down a the sonic every thing was fine. But when I started back up and left the filte can seal went out and started dumping out the oil fast. I was almost home (1000') when I seen no oil presure. pulled into the drive way and shut it down. Then I seen the oil every where outside inside. Filled it back up, fixed the seal frist. And it still running great to this day60-70 psi of oil at speed 20-30 at idle. When I got the truck the eng was unbolted like it was about to be pulled? I just reconnected every thing and its been good to go. So way the army was pulling it out? Who knows why they pull them?

 

[Ronbo]

Keep n informed on what you find, This is how I learn....

 

[OPCOM]

Mine's always had a (very) slight lope at idle. If there is a problem, it does not seem serious.

 

[vtdeucedriver]

Nobody answered a question of yours................. Running it over 50 is fine. I would run my on the interstate between 2300 and 2500 all the time and never had a problem. Your oil pressure is right were it needs to be so everyone else is right about a fuel knock or the compressor. Now that being said, I have noticed that some multi-s make more noise than others. I ran 3 deuces and I think I had them licked as far as maint wise. Each one had their different sounds and its funny because right at the RPM you mentioned is where you would hear it. I believe someone in the past that knew about these engines called it a harmonic knock and that it was normal. But what sucks is that all of us are here diagnosing this Via Internet where it could be just about anything or nothing! This year I went out and listened to a 5 ton that had a supposid rod nock at idle, it was on a Gun Truck replica and the only thing that I learned is that it sounded like a normal Multifuel, Just like mine!!! The GT is still going strong today!!
Now you said your a A&P ( what you work on????) so if your like me ( also one). Tinker with it and let us know what you find!!