This may be a rookie question, but it's a last minute ditch to get a buddy's '98 Cadillac DeVille with a Northstar LD8 back on the road as he needs to leave ASAP for business. I am struggling with the installation of a new water pump. We verified the water pump part #, compared it to the original pump that was removed (with ALOT of force, by the way), and have looked at the water pump housing from as many angles as possible. I still cannot get the water pump to "fit" back into the housing flush and then turn counter-clockwise with the GM tool to adequately seal. Am I missing something here? How much *** do I need to put into this thing to get it to seat into position underneath the tabs in the housing? While doing my best to line up the pump fins with the black tabs so the special GM tool will fit over, and then delicately lining up the pump tabs next to the housing tabs, and finally using a half inch wrench to turn the pump counter-clockwise; the engine starts to move and the pump appears to be shift toward the radiator making it misaligned and NOTHING happens. I'm deathly afraid of putting too much force into this and snapping one of the aluminum tabs inside the housing, and I haven't figured out a way to hold the pump flush while wrenching.

What I am doing wrong? Any tips or tricks that would be helpful? I tried using a screwdriver on the engine side of the pump and prying the pump further into the housing, but was unsuccessful. Do I need a large breaker bar?

 

Are you applying any grease to the seal/o-ring on the pump? That will help. Also, the tool should have a bracket that bolts up to the housing, to keep the tool engaged onto the wp, so it doesn't slip off the tabs while turning. I've not had any trouble installing the water pump on these engines. The pump tool should turn fairly easy. Make sure there is nothing on the surface of the housing that would keep the pump from going all the way in...like the old o-ring/seal, or corrosion.

 

I ended up greasing the o-ring, the inside of the housing, and the tabs on the new water pump. Once I put a long torque wrench on the pump socket, lined up the pump carefully by hand, and turned very slowly, the pump turned counter clockwise with ease. I guess the difficulty was user error.