We heard about a broken down old Cat D2 dozer left to rust in a nearby forest so we went to investigate. It is worn out and sloppy with a suspected blown head gasket, broken rings and one brake not working so it will be a challenge to bring it back to life

 As long as you can raise the blade, you can activate the diesel engine compression release and in gear, move the whole Cat by hand turning the cooling fan. The gearing and leverage make it turn quite easy. Walked my 52' D2 a quarter mile back to the shop when the clutch went out this way. My dad was a cat skinner and showed me this. Works forward and reverse. With one person running the brakes and the other spinning the fan you can turn also. Took about half a day though.  There is something just so cool and amazing about seeing old equipment being rescued after sitting abandoned for so many years. I really love this type of work. Wish I could find equipment like that around where I live I would be all over it! Great video guys can’t wait to see the next one!  Recovery and salvation of old iron is the best thing on YT.
Not only do you get a working item, but the iron is not left to rot.
You do a service to machinery and humanity.
Looking forward to seeing that old beast do some work.
 I grew up with one of those when my parents bought some property in 1980. I got to play around on it as long as I started it myself (as a 13 year old, that was a workout!) Unfortunately the previous owner had a habit of always turning the same way when working the orchard, so that clutch wore out... it was cheaper to buy a D4 than fix the D2 so dad let it go to a mechanic.
 Here's another vote for Squatch253. He's very knowledgeable and seems like a terrific guy. He also appears to be very busy with his day job, helping around the farm (Minnesota winters are brutal), and chasin' skirts. Still, nothing to lose by trying, right I'm also not sure how much he'll be able to help you there in Australia or New Zealand (just guessing from your accents), but it can't hurt to drop him a line if you think you could use his advice on something.