Hello all. I was excited to become a new Caterpillar D7 3T owner when the seller and myself discovered the main engine is stuck. The pony motor starts and runs fine but fails to turn over the diesel. I am unsure of the year of the dozer, but the serial number is 3T21780. It is equipped with an angle blade that is hydraulically operated.

Our plan was to remove the injectors and soak the cylinders with ATF and let it sit for a few days. We discovered we needed a special tool (that neither of us had) to remove the injectors. The seller suggested pouring a couple quarts of the ATF down the exhaust stack and leave for a week or two, before attempting again with the pony motor, or a pipe wrench on the coupling of the engine crankshaft to the forward hydraulic pump. If that fails, we may pull it backwards (blade is down).

The current owner has owned the machine for a brief time and is not familiar with its operation. What direction do I move the forward/reverse lever for reverse travel? What is the gear shift pattern and what gear should I use for the pull attempt to free the engine?

Is there a better technique that we should be using to free the engine?

Also, any information on this machine would be greatly appreciated, including the year of manufacture. Could the hydraulic blade be original or is that most likely a conversion from a cable system?

Thanks!!

Yeah pouring oil down the exhaust won't do any real harm and will stop any further deterioration . Just make sure to have the decompression lever in starting position if you try to turn it over. Towing it forward in 5th gear and jarring the clutch could give you a result if not badly stuck. I have had best results removing the injector and useing adapter, pressurizing the cylinder with hydraulic oil from another tractor. The push rods need to be first removed to let the valves close as the stuck cylinder will have an open exhaust valve. Good luck.

Welcome, another place these engines can stick is the water pump. If it has sat without coolant then that is a possibility. However if it’s had antifreeze in it then probably not. It’s also possible the hydraulic unit in front is your trouble. Just throwing some possibilities out there. Good luck!!

BP.

also main clutch could be froze-so if the tranny is not in neutral that would keep the engine from turning

I think the tool you need is a special deep socket with a cutout in the side for the injector nipple to stick through. Several guys on here have made one by cutting the top off a cheap 12 point socket and welding in a section of heavy wall tubing or a pipe nipple. Finally a cut is made in the socket for the nipple to stick out.

By removing the injectors you will be able to find out how many cylinders have rust, water etc. You can also remove the precombustion chamber of rusty cylinders to get a bigger hole to possibly suck out water etc.

After you have done some cylinder soaking, take the timing pointer cover off and remove the timing pointer (top of flywheel housing 4-bolt cover). This will give you access to the ring gear teeth with a pry bar to start rocking the engine back and forth until you can get full revolution.

If it is rust in the bore you might as well bite the bullet and pull the head, there is no trick you can do to restore the engine to running condx with out cleaning the rings and liner . If you do some how free the engine without removing the rust, and run the engine it will be the end of it. After the head is off then try oil to unstick the eng, so you can remove the piston and clean things up...WA7OPY

Hi, Old Gold Cat.
Me, I'm just a 'pore, dumb bulldozer operator', not a 'fully clued up mechanical type', but about the last thing I would be considering to unstick a stuck engine would be towing the unit to attempt to free it up. If you can't get it to move by more 'gentle' means - like using 'loose juice', maybe 50/50 ATF and diesel fuel, and/or barring it over as Old Magnet suggested - I would suggest that it is time to at least remove the heads and find out why it is stuck before you do any more damage.

Some folks in the past have suggested dumping Pepsi in the cylinders for 24 hours and no longer. This might be fine if you have a way of getting it out again if it doesn't free the engine - like having the heads off.

If you want to have a running tractor, be sure that whatever you do doesn't cause any more damage.

Just my 0.02.

"Deas wrote:

Hi, Old Gold Cat.
Me, I'm just a 'pore, dumb bulldozer operator', not a 'fully clued up mechanical type', but about the last thing I would be considering to unstick a stuck engine would be towing the unit to attempt to free it up. If you can't get it to move by more 'gentle' means - like using 'loose juice', maybe 50/50 ATF and diesel fuel, and/or barring it over as Old Magnet suggested - I would suggest that it is time to at least remove the heads and find out why it is stuck before you do any more damage.

Some folks in the past have suggested dumping Pepsi in the cylinders for 24 hours and no longer. This might be fine if you have a way of getting it out again if it doesn't free the engine - like having the heads off.

If you want to have a running tractor, be sure that whatever you do doesn't cause any more damage.

Just my 0.02.

That is very good advice. Thank you. I have not purchased the D7 yet. The deal I had with the seller was contingent on it running. The dozer is in a remote location on the seller’s property and that complicates things a bit for my working on it. If I could get it to my shop, my options are much broader.

The D7 sat for 7 years and was a good running machine prior. I did discover the coolant very low (or empty) prior to attempting a start of the pony, but not sure how low. I added 6 gallons of anti-freeze before adding water. Between my buddy and myself adding water, I lost track of how much we added, but I believe it could have been as much as 14 gallons. Does anybody know the capacity of this system? Possibly 18 gallons? After filling the radiator, it has remained full with no leaks noted.

With that being said, as Bruce P. pointed out, my trouble could be a stuck water pump. I do want to get the injectors out to evaluate the cylinders (does anyone know the size of the lock nut holding the injectors?) before attempting to bar the engine through the flywheel housing timing cover. I’d like to fabricate a tool as someone previously suggested prior to returning to the seller’s property where the dozer is located.

I considered making an offer on the dozer ‘as is’ and removing the blade and towing the unit in neutral the 6 miles to my shop (pasture and remote gravel) to work on it properly. I’ll probably try to loosen it in a ‘gentle’ fashion before that adventure! I’d rather drive it to it’s new home!

I have greatly enjoyed this site and the helpful suggestions. Thank you!! I feel lucky to have an opportunity to own this machine and certainly don’t want to do any unnecessary damage to it while it’s entrusted in my care.

Does anyone have an idea on the year? The serial number is 3T21780. Possibly 1952 or 1953? Could the hydraulic blade be original? Thanks again.