I would appreciate some input on this one guys: I am changing out the original water pump on my 2005. At first, I thought the supplier had shipped the wrong pump, but then I realized - I hope, correctly - that the pump supplied is a complete redesign, one that appears to do away with the spacer casting and the (2) bolts that attach the pump to the spacer. Of course, the gasket between the spacer and the engine is gone; replaced with a new shape that fits pump to engine rather than pump to spacer.
The new pump has the 'height' of the old pump and spacer, so the long 8mm shoulder bolts fit as before, and presumably the pulley will line up as before also. The pump to engine gasket is a thick aluminium plate with built in rubber gaskets for the coolant ports on either side. Everything lines up. However, when I look at the workshop manual it shows the same update gasket PLUS an O ring depicted between the pump and the engine, concentric with the impeller shaft. The W/M diagram doesn't appear to show the spacer (even though the manual is supposed to be 2003/2005); just the engine block with the new-style gasket plus the O ring.
Before I do something stupid (such as assuming that the O ring is built into the new-style pump if it isn't) could I get some experienced and wise input pleas?

 

I noticed that you have no replies. I do know that the new water pump for the 4.0 has a built in o ring, but you must have a 4.2 so I'm not qualified to help. I hope you get an answer soon. John

 

Thanks, Johnken, I hope others may chime in soon. I noticed that some web sources seem to list the same pump for the entire x-100 range (at least for non-SC) so perhaps the pump was redesigned with that in mind. The new pump, which does have built in rubber around the bearing, and with a possible O ring around that which might press hard enough against the aluminium gasket, will only match to the engine block with the spacer removed. The spacer / old pump gasket is completely different than the new set, and even if it were the correct 'height', the old design would not match up with the engine block without that spacer. While waiting for input, I'll keep digging for info, but I am not about to finish the job including the new thermostat housing etc., only to have coolant pouring from the pump housing!

 

When I did my WP on my 03 this is what I put on it. I bought the cheaper one that came with the unit and just a paper gasket, thought it was JUNK, so I got this which is the same as the factory. Some say that these have the orig plastic impeller. Well I got 90k out of my orig unit and many here also go out around that mileage. Chances are you wont have the car the NEXT time you need a WP.
I got this unit.....Engine Water Pump ACDELCO PRO 252-800 | eBay