On engine failures of this nature (coolant in oil, overheat) it is sometimes difficult to pin point & separate, the cause from the effect.
This Kaw engine has a design flaw (in my opinion) that will permit coolant to escape from a worn water pump and leak directly into the crankcase. A good design would provide a "weep hole" to atmosphere for coolant escaping from a worn water pump (again my opinion). Anything that causes coolant to escape can lead to overheat, which can cause a head gasket to blow. Or the head gasket can fail, allowing coolant to escape. In some cases it is difficult to pinpoint which came first. If the crankshaft and bearings have heavy damage, it is likely that your water pump, or a head gasket, had been leaking slightly for some time before the big event.
Had you ever found the coolant level to be low, requiring you to "top it off", but you never could seem to find a leak anywhere?
My point is that all I know is what you say the dealer has told you, and you have not said what the DAMAGE to the engine consist of.
Long term operation of the engine with anti-freeze contaminated lube oil can do some serious damage to the crankshaft and bearings. If this is what the dealer is finding, he is probably giving you the cold hard facts.
If the engine has suffered no damage to the crankshaft, bearings, or the engine cases, the engine "should be repairable"..............but at what cost? Overheats can crack cylinder heads, or even the engine block. Overheat can cause ruinous warping of the heads and block.
So, based on what you say you have been told, either you incurred some catastrophic damage in the event, or this dealer does not want to risk the possible things that might arise after trying to repair this engine.
I guess I'm saying "Short of seeing the actual damage, I don't know if a new engine is justifiable, but at the same time, I don't know if your engine is worth rebuilding either.

Thanks for your input. The dealer is a fast talking New Yorker prone to hyperbole. He's only informed me that I have a big bill to pay, not with the details. He will call me with the cost and details today (which probably means he'll call tomorrow or the next day, if past performance is an indicator). If the details sound fishy, I'll let you know.

Pat, I hope you don't take this the wrong way, but............
Unless you know either a good bit about engines, or else you know how to "read people", anything he tells you might "sound fishy" considering the mood you are in at present. I know situations like this come without warning and are like a blow to the head from the blind side, certainly enough to sour one's outlook.
I hope everything turns out well for you but as I said before, without seeing the damage first hand, I don't know what shape the engine is actually in.
Get details (and photos if possible) and post all that.
I and others on here can make a better judgement call if we can "SEE" what your dealer has on his hands.

As I suspected, the dealer didn't call me today, and I'd be surprised if he calls tomorrow. The last time he had the tractor, he kept it for three months with no explanation and then sent it back with a new motherboard. I can generally fix a tractor that's not starting, but I know my limits, and this needs a trained mechanic. If I had some information, or photos, as to what the damage was, I could tell you, but as the dealer has it now, and I no longer have access to it. If I don't post here for a few days, it's not because I'm not still communicating, it's because the dealer is not giving me any information. What sounds "fishy" so far, is the dealer telling me I should be "beat up" for not maintaining the tractor when I performed the owner's manual's maintenance annually and the machine ran like a top. When I changed the oil in March, there were no signs of water or anything unusual about it. Other than maintenance, and the motherboard, the only attention this engine has needed in eleven years was a new time delay module which I diagnosed and installed myself last year.

Patrick,

What is this 'motherboard' you have mentioned twice now? Are you refering to a engine computer part? Just curious?

It is the part that handles all the electrical. It looks a bit like the inside of a computer or TV set. I don't know precisely what it does (electronic ignition?), and I presume there's special equipment to test it. Electricity was never my strong suit.

Just a follow-up to my original posts. I called the Deere dealer after not hearing from him for a week. He still doesn't know how much it will cost to fix and whether he can do it. He says the water pump and cam are shot which is not surprising at 1400 hours (especially with plastic cam parts) but he also says the crank shaft is shot which sound dubious. He said he would call me back when he knew, but when I called him back to ask how much a new tractor was, his voice brightened considerably and he had the sales rep on the phone with me in 2 minutes. Given the chimera that will result from cobbled parts, we'll probably purchase a new x720.

Thanks mownie 7, I believe you had it right in that the water pump was worn and potentially leaking into the engine (I did need to top off the coolant from time to time). Who would suspect that a water pump could cause the entire engine to go (if the dealer is telling the truth). Also, a water pump failure would cause the temp gauge to rise while the engine continued to run. I still think crank shaft replacement is dubious, but he has me over a barrel and clearly wants to sell a new machine.

Ultimately, I had 11 exceptional years of service from this machine. I worked it hard and it never complained. I'm still a Deere fan in spite of NYC service deficiencies.

How about buying that new JD from another dealer you might find less underwhelming who will at least give you the illusion that he wants your business?

Unfortunately, he has the state contract and if I want the discount (which is substantial) I have to use him. The sad part of this is that the people who are paying the price are the state's citizens and tax payers. We may see if our state representative can help (or revisit the contract), but I can't risk ticking the dealer off since I have to use him. Believe it or not, I get my parts faster out of St. Louis than in my own neck of the woods.

A real New Yorker would tell that dealer "Yo, I got your customer service RIGHT HERE"

Bet they got JD dealers in Jersey and Connecticut.

If you don't reign in the dealer now it will only get worse... maybe revisiting the contract is the best bet.

***"Who would suspect that a water pump could cause the entire engine to go (if the dealer is telling the truth)."***
I (for one) know very well the damage that can be incurred from running coolant contaminated oil in an engine.
In the case of a component gasket or seal leaking coolant into the crankcase over a long period of time, the damage is particularly insidious in that it does its dirty work without being evident until it is too late for intervention.

mownie,

An elegant way of saying design flaw where the Kaw plastic cam gear was just plain penny wise and dollar foolish.

In garden tractors I prefer mine air cooled... air is free and it don't leak.

The nice thing about liquid cooled engines is that they run at the same temperature Winter & Summer. The temp. gauge is also nice to have. I have 3 - JD 318s and 1 - 425. I love the 318s but the 425 is downright awesome.

Jim