Oil Seal Design for 365/400 for ZF Power Steering Pumps | FerrariChat

Oil Seal Design for 365/400 for ZF Power Steering Pumps

Discussion in 'Technical Q&A' started by Tojo, Jul 15, 2024.

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  1. Tojo

    Tojo Formula Junior

    Apr 12, 2002
    499
    Sydney
    Full Name:
    Tim
    I have a question about the oil shaft seal for the ZF power steering pumps fitted to the 365/400 series cars. The seal is a 17x28x8 size with R5 or DB designation, meaning it's a double lipped double sprung metal cased seal. https://www.ashleypower.co.uk/oil-seals-difference-between-r21-and-r23 for reference. The point of this design is that "the dual spring loaded lips, typically used to separate two fluids but can also be used in high contamination situations to keep out foreign materials and to retain fluid".

    The above seal that was used in these pumps is pretty much no longer available. Websites I have found with them are in Europe, and don't have shipping options to Australia. I'm not finding any of my local bearing shops or online sellers with them. The pumps were mostly used in 1970's BMW's and pretty much all the classic BMW parts suppliers show it as no longer made.

    The pump parts diagram https://www.bmwautoparts.net/en/catalog/parts/75385/0/1329/2160/2350/0/0 shows the seal (item 5) is directly behind a sealed ball bearing, that carries the load of the rotating shaft. Therefore the seal is keeping the fluid in the pump from leaking past it, to where the bearing is, and out into the engine bay. From what I can see they have fitted a seal for separating two fluids, that in this application only separates one fluid. With that in mind can anyone see an issue using a more common R4 or R6 style seal in the pump instead?
     
  2. raemin

    raemin Formula 3

    Jan 16, 2007
    2,341
    Lyon (FR)
    Full Name:
    R. Emin
    Rmmoving the pump is an absolute pain, maybe not worth taking a chance on the seals.

    I bought a seal kit for a mercedes (280sl ?). I know it hurts to spend so much (€50) for a seal a few gaskets and a couple of o-rings, but franckly that's not a part you want to take out twice.

    Are you sure the pump is leaky? In my case it was finally the hose that were leaking next to the pump weep hole. Before jumping to conclusion, I would replace the hoses and pour some proper steering oil (modern ATF is not an appripriate substitue to the original/ thick ATF2 in this case).

    Just my 2 cents.
     
  3. Tojo

    Tojo Formula Junior

    Apr 12, 2002
    499
    Sydney
    Full Name:
    Tim
    The pump hasn’t turned in anger in well over 20 years, and having seen a friends pump leaking after not running in about 7 years, I decided it’s best done while I still have the engine out. So it’s apart and I’m committed now. I tried some searches and found nothing prior to going ahead with job, and just went for it. After I got it apart was when I found the drawings, and most of the seals and Orings being NLA. Aftermarket orings and bearings are no problem to find, but that seal design isn’t common unfortunately


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  4. Tojo

    Tojo Formula Junior

    Apr 12, 2002
    499
    Sydney
    Full Name:
    Tim
    Also, best I can tell is the Benz’s of the era used Febi Bilstien pumps as opposed to the ZF ones our cars have. Happy to stand corrected though. Maybe check your kit against the diagram I linked to and see what seals you have, would be interesting to see.


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  5. raemin

    raemin Formula 3

    Jan 16, 2007
    2,341
    Lyon (FR)
    Full Name:
    R. Emin
  6. samsaprunoff

    samsaprunoff F1 Rookie
    Silver Subscribed

    Jun 8, 2004
    4,457
    Edmonton, AB Canada
    Full Name:
    Sam Saprunoff
    Good day Tim,

    I have not "experienced" this pump just yet and so my comments are simply off the cuff... That said, given your review and the that the seal (item 5 in the diagram), a single lip seal could be used. The caveat here is that it would be possible for liquids or other contaminants to enter from the engine bay side into the pump. How likely is that is unknown, but would be a limitation. If it was a major concern, then it could be possible to substitute the item 3 bearing with a sealed version (the picture looks to be an unsealed version) and so this would greatly minimize the possibility of engine bay liquid entry. This would be my approach, as I think the overall concern about engine bay liquid entry would be low and even if so, would not be maintained... unless the car was submerged... and then there would be far greater issues to deal with.

    Cheers,

    Sam
     
  7. Tojo

    Tojo Formula Junior

    Apr 12, 2002
    499
    Sydney
    Full Name:
    Tim
    Thanks for your thoughts Sam, I think the chance of contaminants entering from the engine bay to the pump is extremely minimal. Bearing 3 that is immediately in front of the seal is a sealed grooved ball bearing, the pic does look unsealed, but the one I removed is definitely sealed, it's pressed onto shaft 1, and in turn pressed into the pump housing, close tolerance fits of course. The only chance of liquid entry would be if that sealed bearing were to have a proper failure, or as you say become submerged!
    I will keep on the hunt for the original seal style, but If I can't get one before I need to refit it, I'll take my chances with a single lip seal. My brain says it shouldn't be an issue, but it never hurts to ask around.
     
    samsaprunoff likes this.

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