[Mister Pontiac]

Originally Posted by avman

...My 8 bolt pump has BOTH the dividing plate and a second plate that I have attached a picture of. It's the plate with the "thumb" that blocks off part of the passages, and you can see it sitting on top of the dividing plate. DO ALL PONTIAC WATER PUMPS use BOTH plates?
I've been told that the mechanic only installed the divider plate, the one with the dome-ish curve that has to be as close as possible to the impeller vanes...

Only the 8 bolt design has the two plates. The 11 bolt design uses one divider plate that must be close to the impeller for proper operation. From your description, the mechanic seems to have installed the plate correctly.

That said, you are probably right. If there was no problem before with the 8 bolt setup, and now you're running that hot with an 11 bolt setup, the problem is there somewhere. You're searching in the right area.

One thought I just had, how fast is the new pump turning compared to the 8 bolt setup? Is the water pump pulley the same size as before? Also probably worth pulling the pump again just to verify that only the one divider plate is installed, and that it is adjusted properly close to the impeller. This will also confirm what type of impeller you have (cast or stamped steel). You may or may not find the problem quickly, but each step gives peace of mind to move on to the next potential problem. Process of elimination.

Hope that helps.