I have the "53 block" in my 1999 HR endeavor. It runs perfect and has not given me a problem. It has about 130k on it, and shows no signs of any problems. The main problem with them is people not letting them warm up or cool off properly, and then they crack.
If you do a little research, you'll find people telling you to "run away" from them. I did all my research and decided to take the risk. I am extremely happy with my choice. Some of the coaches had the 53 block, others did not. My brother and I both have identical '99 HR endeavor's, I have the 53 block and he does not. Both coaches run great.
The crack appears on the side of the block, you can google it and find pictures. If it's not cracked by now it probably won't. I would check it out with a flashlight and see if the 53 is there, and if there is a crack on the side of the block then run away.
If not, buy it and save yourself $10k. Just remember to let it warm up and cool down properly and you won't have a problem. You should do this with any diesel engine anyways. Lots of folks don't do this and they are the ones who ended up with the dreaded crack. Hope this helps. Oh, and we love our endeavor, it's an awesome coach. Wouldn't change a thing.
