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water pump rebuild for 1948 Ponitac


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I got a water pump rebuild kit for my 1948 Pontiac flathead 6 cyl. Upon disassembly, some of the old parts are hardly recognizable. The new main seal on the impeller end is a 3 piece part with 2 brass washers and a spring between, all enclosed and captured in a cup shaped neoprene seal. I can see how the outer edge of the neoprene would seal tight in the hole in the pump housing. But the inner hole of the seal is the brass washer that is a very loose fit to either the old or the new shaft in the kit. Not clear how the old seal worked, which looks very similar but in very bad shape. I am used to seals that seal around the shaft with the neoprene but with this one the the neoprene seals only on the outside and does not touch the shaft. Only the surface of the loose fitting brass  washer touches the shaft. Not sure how the spring helps with the seal, except maybe to tighten on the outer edge of the neoprene. This makes it difficult to verify that the seal is properly installed before assembly and it is not easy to reassemble again since it requires a press to remove the impeller and bearing. Is anyone familiar with this type of seal on the water pump. Apparently, this pump design was very common for Pontiacs over a wide range of years from late 30's to end of 40's. Hoping someone would be familiar with it and tell me what I am missing about how it is supposed to work. There is also a carbon washer between this seal and the impeller, but the hole on it also fits loose on the shaft, so thought it may just be a thrust washer since it was well worn from touching the impeller hub.

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