How do I free an age-seized engine on a D7 3T?

I have over the last several years, come across this situation several times. In each instance it turned out to be the fuel pump. Seems as though water get's into the small gears and they lock up. Those small pumps can really hold up the engine rotation. They all seem to free up fairly easily though upon dis assembly.
Hope it as easy as that for you.

Matt

I like your idea of pouring diesel down the exaust manifold and opening the exaust valves. You want to see the valves are free anyhow. Is there a cover where you could get a bar on the ring gear? If you can rock the crank at all it might be the gear.

The decompression mechanism usually only opens the intake valves. If you want to put it in that way, you need to pour it in the intake. Bumping the exhaust valves would be easier if the exhaust manifold is not cracked or something. Might want to ensure that there's not water in there anyway by cracking the oil pan plug.

I kept filling my stuck 5J by pouring the fuel down the air cleaner intake until I got it to start coming out the oil pan plug. I haven't been back to it to see if it has loosened up in the year or two since I did it.

I tried for two years to free a stuck engine. I told a friend (very old mechanic) and he said "pour in a can of coke or pepsi and turn it over tomorrow". I tried it and it actually worked. I asked a chemist friend of mine about this and he said the soda would break the rust without hurting anything else. Anyway it worked very well for me.
Handhewn

My D2 was stuck from sitting 5 or 6 years. Even though the exhaust was covered and there was a tarp over the dozer water still found it's way into the cylinders. I pulled the head to find most of the valves and seats rusted out and about 8 ounces of water on top of #2 and #3 pistons. I freed the engine with the old FIRE trick. Pour a little Gas and Diesel or ATF in each cylinder and let it burn off for 1/2 hour or so. The gas makes the fire and hot diesel fuel or ATF works it's way down the warm cylinder walls to help loosen the pistons (diesel doesn't burn very well unless it's atomized or compressed). This works every time but unfortunately involves pulling the head.
I would be careful to not pour too much fuel into the cylinders because if the engine is cranked (assuming it's freed up, that's optimism:thumb😊 it could hydraulic lock and possibly break something important and expensive.

Good Luck!

I'm going to try to get diesel onto the pistons in the next few weeks and let it sit a few weeks. Sounds like I should drain the pan and watch for diesel down below. I've also heard of the coke solution (it contains a mild acid), but it seems that in a fairly short time the acid will neutralize and leave water+sugar in the cylinders/crankcase. I'm afraid the water would end up doing more damage if not removed. I might try this after the diesel on an overnight basis.

Since the intake comes from the bottom (see photo), it looks easiest to direct it in through the exhaust, pulling the valve covers and opening the exhaust valves. This also offers the opportunity to inpect the rockers, etc and assess the damages. I'll also drop the transfer pump and check it out.
[attachment=7379]D7 Intake.jpg[/attachment]

OK-I've been on this before for other scenarios, but has anyone ever tried melting beeswax into the cylinder? Maybe gas and ATF // Diesel serve the same purpose, but I have sure had good luck with beeswax on other froze up items.
Put some beeswax on the piston head and heat it with a propane torch-let it melt and see what happens after a short while. I think the beeswax would vaporize pretty quickly once you get it going...not sure about that.

I've seen the powers of pop too. I remember in a chemistry class our female instructor ripped a pop can in half bare handed. All she did was get a nail and scrape a circle on the inside of a pop can and swirled the last drink left in the can for just a few seconds. Ripped that puppy right in half. Try the beeswax first and let us know what happens. My instructor's name was Ms. Ireland. She was a real sweety, if you go looking for her to help. :bounce::bounce: