Series 80 water pump end play


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    The water pump on my ’26 Series 80 seems to have nothing to constrain axial motion of the shaft and impeller. I guess ultimately it’s constrained by the coupling that connects it to the generator. Is that the only thing that determines the axial position of the impeller?

    My concern is that the impeller can slide rearward enough that it’s rubbing on the pump cover. This is certainly possible when the pump is out of the car; I can’t tell if it’s rubbing when it’s installed. Or maybe it’s supposed to do that? The parts catalog points to a washer (C-101424) in that general area, but the illustration isn’t clear. Is it some kind of thrust washer? What does it look like, and how does it mount?


    I think I just found an answer to my own question. A vintage technical reference that I have mentions that reaction forces with the water naturally create a thrust load on the impeller, presumably in the direction away from the cover. In this pump, that load appears to be taken up by the face of the shaft bushing. I believe that washer called out in the parts catalog is present in my pump. I had assumed that what I was seeing was just a shoulder on the shaft.

    Anyway, can someone confirm that I’ve understood this correctly?


    Dan, Sounds like you are on the correct path. Pierce used an “open” impeller, a style which does not develop as much thrust as most others. All impellers have thrust, trying to “climb” into the suction line, like a screw into a nut. However, the open side of these impellers allow some recirculation between the front face and housing, pushing back as a counter force to the suction thrust. The net result is very low levels of axial thrust. The washer you found is probably to hold the impeller in a fixed position, limiting the amount of recirculation to just balance these forces while maintaining pump efficiency.  See you at Gilmore; Herb

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