Reply to blwatson:
Rebuilt the pump on my D47U last summer. Not sure how much different the D6 would be. All parts were available from CAT. Not nearly as difficult as I thought it might be. Getting it removed was the biggest challenge for me. I had a lot of help here and the thread which includes pictures is "D47U Water Pump Leak", just do a search under the Advanced Search section. Hope this helps even though it is not for your D6.
Bruce
The D6B water pump is quite simple to rebuild, I got a rebuild kit from my Cat dealer. It was a great kit except for one thing, the ceramic seal wasn’t included. Not too sure the logic behind that, but make sure you get the seal. I pulled the hardnose off my tractor to get the pump off, being a bare farm Cat, that seemed the easiest. You can’t get the pump off without removing the radiator or the complete hardnose. ( I tried).
The bearings are pretty robust, so honestly, I’d give it a few shots (3-4 don’t overdo it) and run it if it’s not leaking. Check the fan for play when you check the oil to be sure the play is not getting worse.
Good luck
Bruce P.