On a D2 or most any tractor for that matter, the water pump pulley adjusts the fan belt tension. What is your favorite technique for Unsticking a siezed one? How much heat can I apply to it and how about some ideas on how to hold it with wrenches?

After I get the locks off, I douse it liberally with whichever loose juice (except WD40) and let it sit for an hour or so. Then, with a soft aluminum bar and small molecular realignment instrument (5 lb hammer) I begin tapping the adjusting ring, rotating the fan every few whacks, er, taps. After a few times around, I begin tapping against the fillets trying to turn it again rotating every few taps. This is all done with the fan/pump and belt still on the engine. By using an aluminum bar, there's less danger of breaking the cast iron fillets or deforming anything. So far, I've never had to resort to using heat, just a lot of patience instead.

Once you get it loosened, start turning the ring back and forth more and more. Eventually the dirt/rust will break down. If the unit is off the engine, I wonder if the citric acid bath would work?

If the hammer mechanics haven't completely buggered up the lock tabs they are relief drilled to accept 1/4 in. pins from an adjustable side pin spanner wrench.

When I had it off for a year, I had it setting with the impellor down so the threads were up. Make sense? I would go by it every other day or week adn give it another dousing with every popular de-stick spray. Even give it a vibration whack once in a while. I even heated it up until it would make the juices smoke and douse it some more. I even put the one pulley face in the vice and heated it until the juice would catch fire. I tried a couple of molecular re-alignment tools to no avail.
Finally I got to the point where I need it on the engine and put it on with the belt loose.
But it still irritates me!