456 Power steering/suspension pump and lines | FerrariChat

456 Power steering/suspension pump and lines

Discussion in '456/550/575' started by deanhalter, Oct 30, 2016.

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  1. deanhalter

    deanhalter Formula Junior

    Dec 27, 2008
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    Dean Halter
    #1 deanhalter, Oct 30, 2016
    Does anyone have any information on these pumps? I am experiencing a leak on the driver's side of the car near the pump. It may be a line, but I want to have some data in case I need to rebuild the pump.

    It is a ZF pump with the part number 8691 955 160.

    Also, the lines from the pump to the power steering rack and the rear suspension system as no longer available (at least as far as I can tell), anyone have a source for these? I suppose I can go to a hydraulic shop and have one made up, but if there is an OEM one that would better.
     
  2. Cribbj

    Cribbj Formula 3

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    #2 Cribbj, Oct 30, 2016
    Dean, any good power steering shop with import expertise can rebuild these pumps and your steering rack if the seals are leaking. In fact, you can pick up a generic ZF rebuild kit for a Porsche or BMW from eBay and replace the pump seals yourself.

    The lines are trickier, especially the high pressure line because it contains a dampening orifice to limit the NVH produced by the pump.

    The supply (low pressure) line is just normal hose, and it's a known leaker on our 550's, and probably your 456's too. Hopefully that's where your leak is, but on our 550's it "normally" leaks up near the reservoir, not near the pump itself.
     
  3. deanhalter

    deanhalter Formula Junior

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    Dean Halter
    #3 deanhalter, Oct 30, 2016
    Do you know if the suspension line has an orifice in it too?


    It is interesting that there are oodles of pump-to-steering rack lines on eBay, but none of the lines that deliver fluid to the rear of the car...
     
  4. Cribbj

    Cribbj Formula 3

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    #4 Cribbj, Oct 30, 2016
    Last edited by a moderator: Sep 7, 2017
  5. fatbillybob

    fatbillybob Two Time F1 World Champ
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    #5 fatbillybob, Oct 30, 2016
    A longer hose has less NVH which tends to be absorbed in the longer run. I would think the long hose going all the way to the rear would just be hose with no orifice valve. Honestly it seems faster and higher quality to have many Ferrari hoses made than thrying to hunt all over the web for them.
     
  6. fatbillybob

    fatbillybob Two Time F1 World Champ
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    #6 fatbillybob, Oct 30, 2016
    John,

    You are like a genius. Nobody talks about this stuff. Is there something that happens as these hoses age? It seems like the hoses harden with age. I wonder if when we get pulsations through the wheel going lock to lock at slow speeds that were not there when new imply changes in the hose where the tuner orifice valve is no longer tuned to the system?
     
  7. Cribbj

    Cribbj Formula 3

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    #7 Cribbj, Oct 30, 2016
    Carl, I think the pulsations we feel in the steering could be a result of several things:

    1. Drag in various components - mainly the rack?

    2. Natural pulsations in the pump flow

    3. Perhaps the modulating & relief valves chattering a bit as we hit the locks?

    4. Grunge & debris in the system?

    The power steering system has one of the toughest jobs on the car, and it's a system that gets minimal attention.

    Who flushes the system and changes the fluid along with the rest of the fluids? I'd be willing to bet almost nobody.
     
  8. fatbillybob

    fatbillybob Two Time F1 World Champ
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    #8 fatbillybob, Oct 30, 2016
    LOL! I do annually with brakes and coolant. For some reason we eat PS pumps on our vette race cars. My friends all use the turn1 rebuild for racing. I use a stock pump with annual fluid changes. Guess what? My pumps last just fine.
     
  9. fastradio

    fastradio F1 Rookie
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    #9 fastradio, Oct 30, 2016
    We do...and I would expect that most pro shops do.
     
  10. deanhalter

    deanhalter Formula Junior

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    #10 deanhalter, Oct 30, 2016
    John,

    That line has a similar crimp in the middle, so i am guessing an orifice as well. Did you have one made up with an orifice? I would not be inclined to cut my hose to check the orifice diameter unless I know the hose is truly knackered - can you tell me what the orifice size was for the steering rack hose? It is not likely to be the same, but it is a good reference.

    Thanks,
    Dean
     
  11. Cribbj

    Cribbj Formula 3

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    #11 Cribbj, Oct 30, 2016
    Dean, that orifice has about a 4 mm ID.

    I've not replaced the line yet as my car is still a long way from running :(
     
  12. fatbillybob

    fatbillybob Two Time F1 World Champ
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    #12 fatbillybob, Oct 30, 2016
    Dean,

    Those things are "tuners". Orifice length, diameter, hose type and position along length all effect the tuning for reduced NVH. They are like your fingers on a guitar fretboard striking a note.
     
  13. tazandjan

    tazandjan Three Time F1 World Champ
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    #13 tazandjan, Oct 31, 2016
    John- Mine is changed at least every two years using Valvoline Dexron VI. Not something I want to have overhauled if not necessary.
     
  14. deanhalter

    deanhalter Formula Junior

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    #14 deanhalter, Oct 31, 2016
    Agree on the tuning. Given that this is a positive displacement pump at high pressure, they are probably trying to limit the pulsations as already posted. I am not sure how much you need it on this side as my expectation is once the system is at pressure you're only moving fluid when the system load changes as commanded by the anti-roll bar position at the back of the car. This should mean the system stays largely floated on the relief, with all the fluid recircing to the inlet side of the pump.

    I may just have a hose made up as the rest of the system is 1/4 OD line - should be one hell of a damping effect with the 10' or so to the back of the car...
     

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