Just bought an M923 and I have several questions

[DocPA]

new here in Arizona, thanks in advance, just bought an 87 m923. supposedly remanned in maine depot in 2011. two questions, how do i tell if the engine was either rebuilt or replaced? guy told me the engine should have a reman tag on it with info that i cant find, its a natural 250 cummins. no reason to believe the truck wasn't overhauled, there is a tag on the dash passenger side and its in perfect condition but i'm curious about the engine. Also will a tarp and bow set from a duece and a half 14 foot body fit a 5 ton 14 foot body?

 

[clinto]

Deuce is 12', 5 ton is 14', so you'll need the right cover.

 

[Woodsplinter]

M923

Welcome, Doc. There are 3 MV clubs in the valley that can help you with your new truck:

www.desertwarriorsofarizona.com (west valley) Desert Warriors

www.armytrucks.org (Phoenix metro) Arizona Military Vehicle Collectors Club

www.AHMTA.com (east valley) Arizona Historic Military Transport Association

 

[Suprman]

The engine should have a data tag on the timing cover. Drivers side front stand by the front tire look forward you can see it. I have seen them covered with duct tape and painted over. You can just peel the tape off. The tag will have engine serial number and date of manufacture. If the truck has a rebuild tag then the motor may have been rebuilt or replaced. Or it may have been cleaned and painted. Rebuilds are ymmv.

 

[DocPA]

923 A1 Cummins 250 knock

looking to buy an '84 923 A1 with a non turbo 250 cummins. 3400 miles and 1000 hours on it. appears to be in great shape. my only concern because I'm not that familiar with the engine. It is very noisy at idle, like a knock. The owner says its a fuel knock. It doesn't sound like a metallic knock but it's a knock which changes with the rpm. Are these engines normally noisy? Oil pressure is good. No miss. Any info would be helpful thanks.

 

[R Racing]

Yes the Cummins engine are very noisey !!! All of mine have a rocker noise that could be confused with a knock. There stout engines but quiet isn't in there vocabulary lol. But there a good solid platform. If you really concerned make a video and post it .

 

[IsaLandr]

This may seem obvious, but the air compressor on these is also extremely noisy and can sound like lifter tapping or slight knocking untill it runs up to pressure and blows off the release valve. Did you run the air pressure all the way up till the compressor shut off before shutting the engine down? If not, try that and see if the sound changes.

 

[Carlo]

On my M923A1 the only thing that does not make noise is the exhaust! Just standing beside it running you can go death!

 

[DRTDEVL]

Funny thing about those 250s... when running properly under load down the highway, the engine sounds like someone is rapidly hammering on a coconut.

 

[swbradley1]

My M813 is noisy as well, but it's a good kinda noise.

 

[jeepzilla47]

Mine makes a funny knocking sound also. But I have heard several trucks make the noise. Like an odd firing cylinder

 

[Vintage iron]

yes, the Cummins 250 are noise, but the advice on the compressor is smart too. Does it bang all of the time or just noticeable at idle? I have seen low mile motor eat a cylinder from sitting around. It is most likely bad fuel or just gummed up injectors from sitting. put some ATF in the tank to clean out the fuel system and lube everything up. see if that helps. Take the truck for a spin and the ATF will douch everything out. Then see how it sounds before you buy it. There is a lot of things that make these motor knocky, Bad fuel, aerated fuel, water in the fuel and just being cold. Oh, yes the compressor is loud too, but that is a different story. good luck.

 

[DocPA]

I did run the compressor up till cut out and thats not it. I took if for a ride and it runs fine. No smoke, no miss, good oil pressure. The hammer on a coconut is a good description. Thanks for the replies. I hate to pass it up for the price. Its got super singles and bows/tarp, no rust. Who knows if they're going to sell any more of these trucks at auction. Thanks again

 

[1 Patriot-of-many]

I would say normal, there's a big difference in noise between A2's and A1/A0, one of the reasons I prefer the A2.

 

[SLOrazorsedge]

Yup, the A2's run like velvet in comparison to the A/O and A/1's. I have a M923A1 with a new 2011 crate motor and the air compressor has the knock sound. My two A/2's have none of the rock rattle and roll of the non turbo Cummins motors.

 

[GAZ69OK]

Funny thing about those 250s... when running properly under load down the highway, the engine sounds like someone is rapidly hammering on a coconut.

Excellent description. I was thinking the butt end of a drum stick on the bottom of a large coffee can, but I think yours is more accurate. I was hoping it wasn't a knock I was hearing or a bad sound due to a leaky/blown head gasket on cylinders 3 & 4.

Hut

 

[Vintage iron]

I have found that the dual fuel line modification reduces this. The rear cylinders are getting lower pressure and hotter fuel. Adding a supply pump to the fuel system helps even more.

 

[Moosemcnally]

Funny thing about those 250s... when running properly under load down the highway, the engine sounds like someone is rapidly hammering on a coconut.

Best description ever!! The "coconut" noise is unnerving to newly acquainted M923A1 owner!

 

[joesco]

I have the same sound in my M931, but have found that adding about 6 oz of Walmart brand 2 cycle engine oil in the fuel tank works wonders. I have used it for years in all my diesel engines. Buy a gallon of it at Wally World.

 

[Moosemcnally]

I have the same sound in my M931, but have found that adding about 6 oz of Walmart brand 2 cycle engine oil in the fuel tank works wonders. I have used it for years in all my diesel engines. Buy a gallon of it at Wally World.

Can you or someone tell me how that works ? Just curious.