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  1. #1

    Rebuilding difficulty Onan 131-0257 pump

    (I have read Genevatexan's thread from 2011 ) I'm trying to rebuild the raw water pump Onan 131-0257, since it had been previously bodged with rubber seals etc. I have bought new shaft, seal assembly etc but cannot get the parts to fit.
    It seems that my pump has a metal collar in the impellor end, where the shaft comes through (see photo)...this is ~4mm tall and ~<2cm in diameter...is this usual?? This is too small a diameter to permit the ceramic/ rubber part of the seal (E) to move against the face and by the time one puts the carbon seal portion (D) on the shaft, the recess for the retaining circlip is already masked, even before the spring and spring plate are added (B&C: see cutaway diagram).
    Is this "collar" normal or have I got the entire assembly incorrect (plus is the slinger going in the correct place on the diagram)
    Many thanks for your time and assistancepump collar closeup compressed.jpgwater pump diagram 131 0257.jpgparts order compressed.jpg

  2. #2

    Re: Rebuilding difficulty Onan 131-0257 pump

    Will the white side of the seal fit in the pump bore after it is placed in the rubber part? I can’t tell from the photo but I first thought that was part of the old seal but after looking at the seal assembly it doesn’t have the seal made into a cup assembly that got pressed in the body of the pump. Is it possible that someone previously installed the wrong seal assembly? That looks like the cup assembly for the 131-0267 pump.
    Last edited by dsharp; 11-29-2020 at 10:48 PM.

  3. #3

    Re: Rebuilding difficulty Onan 131-0257 pump

    https://www.pumpvendor.com/media/onan/Onan_131-0258.pdfAre those the seal parts that came out that you took a pick of? I would put that pump body in some diluted muratic acid for about 5 minutes before you put the new parts in.

  4. #4

    Re: Rebuilding difficulty Onan 131-0257 pump

    Hi..these are all (seal assembly and shaft) new components...the seal set being 131-0220 and the shaft being 131-0222, all in Onan/ Cummins boxes, as specified in the parts diagram list.
    I'm confused by what people mean by "bore" as, to me, that refers to a longitudinal hollow inside a solid block...so this pump has one bore, but has several diameters along it's length...the shaft can only be inserted from the pulley end of bore...
    The white ceramic seal sits in a rubber cup...this will not fit inside the metal "collar" (seen in photo) sited at the impellor end inside the bore...should it? I presume the ceramaic would face the impellor end and hence make contact with the carbon seal of the next piece of the seal. The position of the slinger in the assembly also eludes me in the assembly order....
    thanks for your help and questions

  5. #5

    Re: Rebuilding difficulty Onan 131-0257 pump

    the 2 parts of the ceramic seal...ceramic part and rubber cupceramic seal.jpg

  6. #6

    Re: Rebuilding difficulty Onan 131-0257 pump

    I can’t tell from the photo but, the part that is down in the pump from the impeller side. Can you tell if that is part of the brass body or a cup shaped piece of sheet metal? All of the pumps that I have seen have a bore or recess machined in the brass pump body that the ceramic puck and rubber cover sits in. The ceramic with rubber should press in with very little finger pressure. Put a little silicone grease on the rubber to help it slide in. The slinger goes next to the bearing and goes in from the bearing side. Was the ceramic puck and rubber sleeve down in the collar when you took the pump apart? You need to get all that crud cleaned out of the impeller side before the new seal goes in.
    Last edited by dsharp; 11-30-2020 at 09:25 PM.

  7. #7

    Re: Rebuilding difficulty Onan 131-0257 pump

    Hi...it might well be a cup shaped piece of metal, but is rigid. As it's only~1mm thick I think it unlikely to be cast with such precision. Furthermore, on scraping it it MIGHT be steel/ SS rather than bronze, but difficult to tell. Hummm!

  8. #8

    Re: Rebuilding difficulty Onan 131-0257 pump

    ..oh...there was no ceramic seal before...had been bodged/ bubbad with a rubber and spring seal glued in :-)

  9. #9

    Re: Rebuilding difficulty Onan 131-0257 pump

    I would send it to depco pumps and have it evaluated. No telling why the thing was all boogered. Is there a company like them in your area? You just can't replace parts sometimes.
    Scott
    41C117 "Hattatude"
    Port Canaveral Florida.


    Marine Electronics and Electrical Products Distributor.

  10. #10

    Re: Rebuilding difficulty Onan 131-0257 pump

    Unfortunately I'm in Antigua, so access to parts etc not available locally. Have to import from States with upto 60% duty (even carriage is included!). Sending by Fedex from here to Depco etc and have returned would cost almost as much as boat is worth (maybe slight exaggeration, but you get my drift!)!!!
    Possibly put in a March LC-3CP-MD?

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