Just completed the install on replacement water pump on my 4.2L. Originally put a 2 piece A/M pump about 30K (5 yrs) miles ago. The old pump had a shiny metal impeller and showed to evidence of cavitation with Prestone Dex-Cool. Replaced with the AC Professional Part 252-800 sourced online for $61. The impeller appeared to be rough casting of metal. The pump had rubber cone at center and had a metal gasket with thin RTV like sealant around the openings for the water flow on each side. Install was easy and it seemed to work as intended. Bled the system and refilled after over night wait. Was surprised at the amount of coolant that weeped from under the car after I finished. The pump, upper hose and drain were dry but, still had the old coolant drops on floor to cause concern. After close inspection again, buttoned it up and ready to drive. The belt on alternator pulley always ran 1 groove back from edge rather than cover the pulley entirely, the belt now covers the pulley as it should. The AC Delco appears to be Top Quality.

 

Well done. I will make a note of that AC Delco water pump for future reference....

 

See my previous thread with my issue with a new two piece water pump.

The single piece AC-Delco part is definitely the way to go. No issue since I installed mine.

https://www.jaguarforums.com/forum/x...-181907/page2/

 

I also used the AC Delco pump and would recommend it at this point.
My writeup on the R&R of pump and pulleys with a complete list of parts is here in my working thread