M816 wrecker- why trans cover off?

[johnnyg8]

Dear Steel Soldier friends,
I bought the M816 5-ton Student Driver wrecker from Ft. Leonard Wood, MO last year and am just getting around to trying to get her running again. Seems the Cummins 6-cylinder NHC-250 engine was locked up from sitting? Would not budge last fall with bar on engine or attempted prysing via flywheel.
I removed the injectors and poured 2 gallons of Marvel Mystery Oil amongst all the 6 cylinders and it has soaked for 3 months. We will try to bar the engine again and see if it will move now.
An expert says the 6x6 family is bad about sitting around and then getting water into their exhaust stacks which goes down and then rises from the bottom of the muffler up into the engine. He suggested i remove the Allen plug from the BOTTOM of the muffler- says often water drains out then.
He said perhaps the oil pan can be removed and the heads, one by one and then it can be determined what is locked up- says maybe a sleeve kit or two may do the trick, but a rebuilt engine is better. The wrecker only has 24,000 miles on it.

Also for some reason the recovery school's maintenance guys at the base had taken off the gear shifter and the plate in the floor above the transmission. Why? Is there a common reason why they'd do that? To change the clutch? Access the trans gears?
They had removed the front axle of the rear tandems, I guess for towing it.

I appreciate anybody's insights into whether or not the engine will run again or a rebuilt one is better, and about the removal of the trans shifter and cover.

Johnny from NC

 

[jcappeljr]

I had a m813 about 10 years ago,I had the same problem. We pulled the oil pan, and removed the piston ,and replaced 1 liner. The truck ran perfect after that.

 

[NDT]

If you have water in the cylinders, even if you can get the motor to turn over, the rings will be stuck and the engine will not run very well. Usually if an engine has water inside, you can crack the oil drain plug and water will come out first. Also the ends of the injectors will be rusty.
If someone went through the misery of taking the top off the transmission, you can bet they did not do if for fun. Something major is wrong with the transmission, which is a bit unusual.

 

[timntrucks]

seams like it might have a clutch problem .. maybe its stuck and that makes it look or feel like the engine is froozen. just a thought kinda like hoping it would be a simple fix.

 

[johnnyg8]

Thanks a lot, guys,
We'll try to get out the plug at the bottom of the exhaust and also see if a bar can do anything. I, too had wondered if it could be hung between two gears as I've heard they sometimes did. If the clutch is hung somehow it seems logical that they may have been getting ready to drop out the transmission and get to the clutch.
It's a mystery- when I'd taken off the valve covers a few months ago everything looked brand new in the top. Unfortunately after I'd removed the injectors and filled the cylinders with Marvel Mystery Oil, then set the valve covers over the rocker arm boxes, somebody left open the hood and moisture got to the valve springs. It may not have hurt anything.
We'll see now that it's at my farm and not sitting in the wrong parking lot...
I guess we can start pulling heads after draining the oil and removing the oil pan. How can we tell which piston(s) are stuck if any? Will there be something visible? Will we end up tapping upward on rods with a hammer and fat punch from below after removing rod caps?

 

[nk14zp]

Just turn your back and walk away .O yea whats your add so i can remove this junk?

 

[andyindy]

Do you think the tranny is toast and thus locking the engine? If it were me, I think I'd start with the trans and make sure that wasn't it before I tore into the engine. Just my worth. Keep us posted!

 

[nk14zp]

Have you tryed to turn it over with the clutch pushed down?

 

[halftrack]

seams like it might have a clutch problem .. maybe its stuck and that makes it look or feel like the engine is froozen. just a thought kinda like hoping it would be a simple fix.

Ditto. Had this problem all the time with farm tractors that sit around. Clutch is stuck to the flywheel making you believe it is a frozen motor. . A good and simple way to check this problem is to put the transfercase in neutral and see if the truck can be towed freely.

 

[johnnyg8]

My friend at the local Truck pro advised this morning to mash the clutch in (mechanics who'd tried before to turn the engine SAID they's done that), and then try to turn the yoke on the tail of the trans by hand. He said if I could not it's in the trans.
If in the trans he said to take off the trans top plate (possibly WHY the military mechanics had removed the floor plate and gear shifter above the trans), and then use the gear stick and go through the shift pattern and get to neutral. He said the sliding clutches could be stuck which means pulling the transmission.
Thanks to all of you. -Johnny

 

[johnnyg8]

Thanks- that is exactly what I thought originally and the 'mechanics' (shade tree) denied it was possible. To me your explanation is perfect.