420 Water Pump Questions
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    420 Water Pump Questions

    The water pump on my 1956 420 tractor has failed. I was embarrassed by how much play had developed in the bearing, but in my defense, it made no sign it was going until yesterday. The ball bearings disintegrated. I pulled it apart today to see if it was in good enough shape to be rebuilt, and I noticed that the impeller vanes and the interior surface of the pump are tapered. If I put a straightedge across the surface of the housing, the diameter at the opening would not be even close to flush with the straightedge. I suspect that this might have been caused by the play in the bearing that allowed the shaft to rock, but I have no idea if that's the case, or if it's supposed to be that way. Based on the area that shows contact by the impeller, it looks like it may have been made that way, as it seems too even to have been caused by wear. If it's wear, then I'll need to replace the pump because there would be no easy fix to the housing.

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    Could anyone who has rebuilt one of these tell me if these pumps are made with this taper? Does anyone have any experience with the aftermarket (I expect Chinese) water pumps for these, in case I need one?

    Thanks,

    Stephen Barner
    Bolton, Vermont

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    Brownie919's Avatar
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    I would just go A&I aftermarket through your local Deere dealer. Its about $250 with a 1 year warranty.
    You can get the same thing on EBay from the same manufacturer a little cheaper but if theres an issue you don't have the support.
    2001 4300 SyncReverser 430 Loader/48 Backhoe
    Walker MC20 Zero Turn

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    A follow-up JD 420 water pump rebuild

    Further investigation led me to believe that the taper is indeed part of the design, and not due to wear. I proceeded to order a rebuild kit and install it. I ended up re-ordering the kit, as I found that the seal that was included is not the same as the original style and is slightly thicker. The original seal contacts and seals against the impeller and allows the impeller to be removed without damaging the seal. The new seal is a press fit on the impeller shaft, making it impossible to remove the impeller without damaging the seal. Unfortunately, it was only after installing the impeller that I realized that the new seal takes up more space on the shaft than the old one, hence it was destroyed getting the shaft back out. I needed to put the impeller on a lathe and turn down its seal face several mm to make enough clearance for the seal out of the second kit I purchased.

    Getting the impeller and the seal on without damaging the seal, since they were both now press fit to the shaft, was a bit of a trick, but I managed it and I will say that the design of the new seal looks quite good in terms of actual functionality. The tractor is back together and, thankfully, there are no leaks. The tractor got a good workout with our first snow of the season, last week.

    The benefit of rebuilding the original is that I maintain a bit of the tractor's originality and, even with purchasing two rebuild kits, I have less than half the cost of a Chinese replacement into the repair. On the other hand, if the pump starts leaking again, I will wish I had taken the easier route. Replacing a water pump on one of these tractors takes several hours to complete.

    The skinny is that the current rebuild kits are not turn-key with these pumps. If you are in a hurry, or don't have the tools or experience to do some re-engineering, just buy the complete pump and be done with it. The folks making these replacements available are doing us a favor and deserve to be rewarded.

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