I have had to replace 3 water pumps in the last 9 months. 2 rebuilt and 1 AC Delco new. The new one failed after 1000 miles. Any ideas on what else could be wrong. I have a reliable certified mechanic that has replaced pumps on other duramax diesels.
What's failing on them? Most common thing is to spin an impeller or gear off the shaft. Happened to me. Danville sells a pinned pump and DHD sells one with some kind of composite impeller or something. There's a few companies that offer pumps that have the impeller and gear welded to the shaft, but I've heard of those failing too.
The new pumps begin to leak after a few hundred miles. I get a low coolant warning. They are not leaking when I leave the shop. My mechanic is certified and has experience repairing Duramax diesels, including replacement of water pumps.