I have a 1956 D7 with a stuck engine. It hasn’t been started in about 6 years. Initially I thought the starter was bad because it smoked when I tried to turn the engine over. I had the starter rebuilt and purchased new batteries. That didn’t solve the problem. The ground terminal on the battery melted when trying to start the dozer with the rebuilt starter and new batteries. I thought about removing the radiator and hydraulic fluid tank to gain access to the crankshaft pulley so that I could manually rotate the crank using a large socket wrench and pipe for leverage. Instead I used a tool that I made using a starter mounting flange, a pinion gear, and a shaft with a welded nut. I then used a 1/2” breaker bar, 1-1/8” socket, and pipe for added leverage to turn the nut, pinion gear and flywheel. When I wasn’t able to turn the flywheel using the breaker bar, that confirmed that the engine was “stuck”. I removed the injectors and valve covers. I didn’t see any rust or water. There was a thin coating of oil on the components under the valve covers.  I then sprayed PBBlast into each cylinder. After unsuccessfully trying to manually rotate the flywheel I then added a cup or more of Lucas Oil treatment diluted with mineral oil to each cylinder and let that sit for two days. I tried again to manually rotate the flywheel but to no avail. I made sure the clutch was disengaged and the transmission in neutral.After unsuccessfully moving the flywheel with a breaker bar I then resorted to using a come along and pipe for leverage and ended up breaking the end of the breaker bar. I then used a large adjustable wrench, a pipe for leverage and the come along, and left things in tension. I plan on getting back to the dozer in a couple of days.The large adjustable wrench is all I had left in my arsenal of tools. I can see that the wrench doesn’t have a firm grip on the nut. Anymore cranking on the come along may end up stripping the nut. I’m thinking about making another tool by welding a 1-1/8” 12 pt wrench directly to the leverage pipe.A question I have is can I access the underside of the piston and cylinder by removing one of the side plates? If so I could I then spray lubricant into that area? Any help, insights and responses greatly appreciated!

Hi,
did you note any back and forth movement in the flywheel to indicate if it may be something simple like the water pump or other accessory being seized--flywheel movement in this case would prove back lash in the timing gear drive train.
If no backlash then one or more pistons are stuck in the liners--back and forth force will likely have abetter result than pulling in one direction--be aware excessive force on the big bar may shear off a ring gear tooth with disastrous results.
You can access the lower end of the engine thru the side covers--I have done an in-chassis overhaul of one of these at the Dealer way back--we fitted new liners pistons and big end bearings which were accessed thru the side covers--expect some knuckle skin to be removed.

Before you break anything major I would suggest to remove at least the exhaust manifold and see if water has entered via the exhaust system and hopefully not via cracked heads , rusted thru pre-chambers or liners.
Good luck.
Cheers,
Eddie B.

Thank you Eddie.

I’m not sure if there is any movement in the flywheel - can’t see the flywheel. And I don’t detect any movement in the fan or in the universal joint. I’m going to take the side covers off and inspect and lubricate as much as I can. I’ll also remove the exhaust manifold and post some photos.

we have freed a stuck piston by filling the cyl with diesel and placing a block of wood in on top of the piston each day give the block a love tap and top up the diesel it worked all we did was hone the cyl and fit new rings every thing else was fine.

I attempted to fill the cylinders with lubricant and was shocked to see that 2 gallons was not enough to fill even one cylinder. Where was all that lubricant going? The coolant level was fine when I checked it a few days earlier. How big are the bores on a 17A? There were no signs of leaking fluids after attempting to fill the cylinder??

Hi,
the D339 engine is a 4 cylinder, 5 3/4" bore by 8" stroke unit and is reportedly 831 cubic inches in capacity by the spec. sheet.
I guess that equates to around 207.75 Cub Inch. per cylinder.
Cheers,
Eddie B.

The oil level on the dipstick didn’t appear to change. I’ll have to check it again. What’s the bad? Too much clearance on the rings? It seemed to run fine when I ran it last. If the exhaust valve was open then might the lubricant be in the exhaust manifold?

Attempted to remove the exhaust manifold today but wasn’t able to completely separate it from the block - it’s hung up on the air intake manifold. The air cleaner will have to removed and I didn’t have time today to do that. I did however managed to pry the exhaust manifold away from the block about an inch or so. In doing so I noticed significant amounts of debris at each exhaust port. My guess is that the ports were full of rodent nest debris. It’s possible that some of that debris is responsible for jamming the engine. I plan to finish removing the exhaust manifold tomorrow and will take photos of the debris and post them. I still don’t no where all the lubricant went. It looks like I’m moving towards removing the heads.