hub oil leaks

     My 1973 Haf. awoke from her 25+ years hibernation, after doing a few bits & pieces got her on the road last year.
     I changed the leaking wheel hub  oil seals  [part no. 900.3805] but did not find the O-rings [part no. 700.] shown in the parts manual, nor could I see any obvious location for them.
     Three  rebuilt hubs seem to be leak free, but the rear nearside hub continues to leak after several new oil seals [from different sources] and rebuilds.The ground diameter showed no signs of rust, the slight black stain from the original seal was polished off with very fine wet & dry paper.
     I hope that somebody can advise me about the O-rings or how they cured the same problem.
     Thanks Graeme.


  • Hi Graeme,
    You are not the first to run into this problem, nor will you be the last..
    Anyway, it's easy!
    When you have dismantled the hub which i am sure you can do blindfolded by now!
    Hold the hub flange (the bit with the studs to hold the wheels) in a vice by the studs. Use a blowtorch to heat the ring on which the oil seals inner diameter runs on.
    After a short while - i.e. not a lot amount of heat, it should start smoking and "pop" it will suddenly lift itself off the back of the hub!
    Basically, under that ring is where the "o" ring fits and heating the ring causes the "o"ring ro expand and push the ring away giving you an access gap to lever it off if it doesn't want to just slide off.

    Clean up surfaces. Put a little bit of red rubber grease on a new "o" ring, put it on the shaft. Put the metal ring on and using a suitable piece of tubing, tap it up against the side of the hub flange and then reassemble the hub.

    Take special care with setting the bearing preload using the appropriate shims as it has a huge impact on the amount of friction that saps power if you get it too tight and will leak oil if you get it too loose.
    You can make yourself a tool for checking the bearing preload by getting a piece of wood or metal with two holes to fit two of the wheel hub studs and which sticks beyond the hub flange on one side. Make a notch in the tool which is 9 cm from the axle centre. Hang a 1kg bag of sugar on a piece of string from here. The arm should stay in a horizontal position if left to itself, but should require very little extra force to make it swing down.

    Post back if you need more explanation / detail etc.

  • Thank you John for your detailed reply. After asking for advice, I contacted Haflinger Technik who were most helpful and gave similar advice to John's. I purchased the parts and did the repairs as described. She leaked oil just as badly as before !!!!!                                                                                          I dismantled it again, sealed the openings on  the casting and pressure tested it under water. [about 2-3 psi]. A stream of bubbles came from the tapped hole which  secures the oil deflector, and a very small crack adjacent  to it.     I ground out the crack with a dermal and repaired with low temperature aluminium brazing rod, cleaned up and  re tapped the hole. I then re- assembled the hub. I have now done about a hundred miles and she is not showing signs of leaking from the hub.                                                           thanks again,                                                                                                   Graeme
  • Well Done!
    Good idea to do the pressure testing, but a pain to have to make the blanks to seal the holes.

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