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Power steering blowing the steering rack seals. -94 456 GT

Discussion in 'Technical Q&A' started by 456 koirra, Oct 18, 2009.

  1. 456 koirra

    456 koirra Karting

    Aug 18, 2005
    95
    Finland
    The steering rack of my 456 GT started leaking suddenly and a lot from both ends. I took the thing out, got all the seals replaced and put rack back in.
    At first for the first few km everything was fine, until the oil got warm or something.. and the thing started leaking from the both ends and really a lot again.

    Any idea what is wrong?! Sounds like there is for some reason too much pressure generated but why?

    All ideas appreciated!!
     
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  3. finnerty

    finnerty F1 World Champ

    May 18, 2004
    10,341
    #2 finnerty, Oct 19, 2009
    Last edited: Oct 19, 2009
    Excess air in the system?

    Have you had the circuit fully air-bled? If not, I would have that done. That is the simplest cause and fix.

    If that's not it, there may be a problem with the pump or pressure regulator which is allowing too much pressure to build up.

    I'm assuming that all the sealing surfaces were properly cleaned and inspected for defects when the seals were replaced ---- otherwise, this could cause leaking as well....
     
  4. 456 koirra

    456 koirra Karting

    Aug 18, 2005
    95
    Finland
    Thank you very much for your reply!!

    Yes, changing the seals was done with great attention to detail. And the leak, once it starts really is plenty, I leave a rude lines of oil (one from each end) behind when I am driving. Just like it was before and the start of the leakage earlier was also abrupt.

    On the manual it is said that the air inside the system is eliminated automatically during the operation so I just did a couple of full turns before I started driving. I wonder if I should have done more, or something else as the system was completely empty before?

    Any hints on how to check the pump or the pressure regulator? Please.
     
  5. finnerty

    finnerty F1 World Champ

    May 18, 2004
    10,341
    #4 finnerty, Oct 20, 2009
    Last edited: Oct 20, 2009
    Hmmmm.

    Since the system went completely dry (out of fluid), much air surely got into it. I would think it would take more to bleed it than what you have done. Generally, with all PS pumps, you need to jack up the front end (so the front wheels are off the ground), start the engine, loosen the cap on the fluid reservoir, and crank the steering wheel fully left and right several times to purge the air out ---- sometimes, a special vacuum procedure must also be done to get all the air out. Be careful when you do this as fluid can gush out the top of the reservoir if there is a lot of air present --- best to have a friend turn the wheel while you carefully loosen the cap so you can tighten it back up quickly if it gushes!!

    As for how you check the pump and regulator on the 456, I'm not sure. There will be a test connection or port somewhere where a pressure gauge can be hooked up ---- any good auto service shop who works with transmissions and such should have the proper equipment and knowledge to check the pressure for you.

    I've never done this on the 456 specifically so I can't give you details there ----- my comments are really just for PS systems in general.

    If you want details about how to check your system, you may want to post your question in the model specific "456 / 550 / 575" section. Someone there will likely have direct experience and expertise with the 456 pump and how to check it.

    Good Luck
     
  6. PAP 348

    PAP 348 Moderator
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    Dec 10, 2005
    86,831
    Mount Isa, Australia
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    Pap
    Im with David on this one. There must be a blockage in the high pressure side. Sticking/blocked relief valve maybe. :):)

    Maybe its crap or old seal material stuck in the high pressure hose causing a restriction or the hose itself has 'closed up' internally. :):)

    I would investigate the relief valve is not blocked first, then check hoses after that. :):)
     
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  8. 2NA

    2NA F1 World Champ
    Professional Ferrari Technician Consultant Owner

    Dec 29, 2006
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    Tim Keseluk
    Relief valve.
     
  9. It's Ross

    It's Ross Formula 3

    Jul 30, 2007
    2,018
    Barrington, Ill. USA
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    Ross
    I'm no expert on your system but can tell you air wont cause the seals to go. Air is compressible so if anything would reduce pressure. You will also hear the pump cavitate when there is air in the system.
    What is the recommended fluid? Are the new seals compatible with the fluid used?
    I've seen lots of hydraulic failures on German cars due to use of incorrect fluids. It isn't usually sudden but that's all I've got for you.
    Good luck
     
  10. 456 koirra

    456 koirra Karting

    Aug 18, 2005
    95
    Finland
    Thank you all for the replies!

    I will try to find the pressure relief valve, ask 456/550/575 section and keep you posted!!
     
  11. garybobileff

    garybobileff Formula Junior
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    Feb 5, 2004
    772
    San Diego CA
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    Gary
    OK, guys, let's get back to basics here. The likely hood that the reason the rack started leaking was leaky rack boots. This was not disclosed when this thread started, but that is the typical reason for leaks in a 456 rack. Ferrari has replaced the rubber rack books with a semi hard plastic style, that doesn't work. The new style boots do not stretch or compress enough, and they don't clamp well, and they start to crack after just a few weeks of use. The substitute parts are garbage. I am going through that same problem currently, and I am searching for rubber boots that will work. I will not rule out a check valve problem on this thread, but, it seems strange that his newly resealed rack leaks again, just like I am experiencing.
    Gary Bobileff
     
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  13. PAP 348

    PAP 348 Moderator
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    Dec 10, 2005
    86,831
    Mount Isa, Australia
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    Should the steering rack boots fill with oil mate? :confused::confused:

    When oil leaks into the rack boots its an obvious sign of leaking rack seals, isnt it? :D:D

    I would like to think that the old rack seals were worn, leaked and were replaced with new seals................and someone fitted the seals in back to front or pinched them causing this leaking issue again. :):)

    But..........the OP did state that both rack ends started leaking oil out a lot of oil and it happend suddenly. Obviously blew out the old seals. New seals fitted and were ok for a few km's before they blew out again and it started leaking a lot pf oil again. :):)

    Id say there is a relief problem there or a blockage somewhere in the system. :):)
     
  14. garybobileff

    garybobileff Formula Junior
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    Feb 5, 2004
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    Gary
    Point well taken, but a further description and analysis of the problem needs to be discussed. Are the boots filling up with pressurized oil? Are the possible plastic boots loose and leaking and not clamped securely? The plastic style boots have a tendency to need re-tightening several times until they "crush " into the surface. Similar to some types of silicone water hoses that will need several tightenings until they finally crush down to stop leaking.
    Gary Bobileff
     
  15. 2NA

    2NA F1 World Champ
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    Dec 29, 2006
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    It seems that the primary function of the boots is to keep dirt away from the seals and the polished surface they ride on. If there is enough oil getting past the seals to make a puddle, I don't think the accordion style boot is going to keep it in.

    If the seals are failing right away either:

    1. The rack surface is scored and nothing will seal against it.

    2. The seals were installed wrong (or the parts were bad).

    3. The system is under more pressure than the seals can handle due to a blockage or mechanical failure of some kind. Hydraulic systems are typically protected by a spring-loaded relief valve to make sure that won't happen. It is possible that it isn't doing it's job.

    4. There is some as-yet unknown other cause (I doubt this but with a Ferrari anything is possible). ;)
     
  16. Bonaccorso

    Bonaccorso Rookie

    Oct 5, 2009
    7
    Orange County, CA
    Full Name:
    Matt
    I haven't looked at the Document in a while but i do believe that the steering racks were a recall. so Before any repair is done call and see with your VIN if this applies to your vehicle at your local dealer.

    However i have replaced them under warranty before.
     
  17. 456 koirra

    456 koirra Karting

    Aug 18, 2005
    95
    Finland
    Thanks a lot for your replies!!

    To cover the rack ends I just used the old boots as they seemed fine and to me. Earlier there were not a drop coming out and the leak really started suddenly, also earlier, from the both ends and is plenty. With plenty I mean about a tankful per 4 miles of suburb driving. by the way, I guess that the pump goes bust if I don't stop to fill up the oil every few miles? I use the ATF recommended but would not like to drive any car anywhere like that.

    After replacing the seals everything was fine for the first a couple of miles, perhaps until the fluid got warm or something, could that indicate something?

    At the moment I would really like to check the relief valve but cannot find it :(

    On the 456/550/575 section there are yet no replies regarding the relief valve location.
    Should I be able to find it from the link below?

    http://www.eurospares.co.uk/partTable.asp?M=1&Mo=568&A=1&B=31302&S=
     
  18. PAP 348

    PAP 348 Moderator
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    Dec 10, 2005
    86,831
    Mount Isa, Australia
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    Very good sir! ;);)

    I thought about a scored shaft, but the rack is leaking from BOTH ends. I doubt both sides of the shaft would be damaged at once and cause it leak at the same time. :):)

    I also thought of the new seals being installed incorrectly, but then that doesnt explain the 'sudden' leak from both sides before the rack was pulled apart. :):)

    It still seems to me there is too much pressure in the system which has blown the old and new seals out. Or the extra pressure is just pushing oil past the seals. :):)

    I fit and deal with a lot of oil seals at work. When there is too much pressure in the system, it will blow the seals out or push the lip seal down and oil will run out anyways. :):)

    They are my thoughts anyways. Relief issue or blockage somewhere. :D:D
     
  19. 456 koirra

    456 koirra Karting

    Aug 18, 2005
    95
    Finland
    I just spoke with the mechanic who changed the seals. He figured that there is a possibility that air could damage the seals if it escapes abruptly as the oil then hits the seals harder than they are meant for.

    I tend to think that it would be a blockage/relief issue but still need to find where it could be. :eek:

    One another thing came up though! could be meaningful especially as the possible recall issue mentioned. There was a 2 pin connector going to and a magnetic valve of some kind on the steering box of the rack where also the steering rack was connected to. Would anybody know what are these for?!? I did not find anything about it on the eurospares parts diagrams.
     
  20. PAP 348

    PAP 348 Moderator
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    Dec 10, 2005
    86,831
    Mount Isa, Australia
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    I have never heard of that before. :D:D

    Maybe your mechanic is clutching at straws me thinks? :p:p

    Sorry I cant tell you where the relief is. My guess is in the back of the p/steering pump. But im not 100% sure. :):)

    Id say that is your p/steering pressure switch. It 'hardens' up the steering by reducing oil flow to the rack so the steering is not as light as you driver faster. This makes for safer steering at high speed. :):)
     
  21. sowest

    sowest Formula Junior

    Aug 18, 2006
    899
    This is an interesting problem. It sounds like the rack ends are leaking as the car is being driven straight ahead. I was going to suggest that there shouldn't be pressure in the rack when it is at rest and only receives pressure to move the rack when the spool valve applies pressure to one side or the other to turn the wheels. Then it occurred to me that the whole system may be under full pressure until the spool valve vents off pressure to one side. It would seem odd to me to keep the entire system under pressure all the time, but this is Ferrari after all.

    I can't see that the the rack boots are supposed to contain hydraulic pressure. Even a very small pressure would blow them up like balloons.

    I also seems odd that good, well fitted seals would fail because of pressure. My shop press works, hydraulic cranes work, back-hoes work. Is the pump belt driven? It would seem that the belt would fail if there was really a failed relief valve that was allowing uncontrolled pressure. The pressure check valve is very likely a spring loaded ball or plunger that is incorporated into the pump casting.

    It would be very interesting to fit a pressure gauge into the system. When the engine is running and the steering is at rest does fluid flow back through the return line?

    Well, no solutions, just some (possibly worthless) thoughts on the subject...;>)
     
  22. oldcoin

    oldcoin Formula Junior

    May 1, 2006
    258
    Reno NV
    Full Name:
    Tony Mitchell
    Some years ago, We replaced the power steering rack on my wife's 1984 Jaguar XJS. We got a rebuilt unit and installed it. The instructions that came with the unit warned us to replace the power steering hoses and flush the pump and that failure to do so would void the warranty. We did not heed this advise and a month later the rack was leaking profusely.

    2nd go round, we replaced the rack with another rebuilt from the same source and replaced the hoses and flushed the pump. Never leaked since.

    Apparenty as the hosed deteriorate from the inside, there are tiny particles of petrified hose that circulated thruout and get caough in the seals and score them creating leaks

    Just my experience.

    Tony
     
  23. 2NA

    2NA F1 World Champ
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    Dec 29, 2006
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    Jaguars are notorious for leaky racks, I've changed out a bunch of them over the years.

    Another reason I'd never own an XJS.
     
  24. 456 koirra

    456 koirra Karting

    Aug 18, 2005
    95
    Finland
    Thank you all for the replies! I really appreciate them!

    Then I took the car to my mechanic as he was able to spend some time on my car and me. I really appreciate this as I am technically not that experienced, yet.

    We decided to check the seals, rebuild the system again and deair the system according to the procedure explained by finnerty as I was unaware of such procedure when I installed the first rebuilt rack.

    The seals in there turned out to be fine but we put in new ones in again. We flushed all the hoses and the pump, cleaned the tank and put everything back together.

    Again, everything seemed to be fine, but only until we really tested the system with lock to lock turn. To the other direction we turned all the way and that side started leaking.

    Now the pump is off and on the way to an expert.

    On the 456 there is the self leveling system which shares the oil and pump with the power steering. However, these run in separate loops and do not seem to cause the problem. I have not had any alarms from the self leveling system, nor any leaks which the shocks are notorious for. I would assume that if the pump was producing too much pressure, these would leak easy but still really hoping that the problem would be the pressure relief valve. New filters have been ordered.

    Will keep you posted.
    All ideas and comments appreciated!
     
  25. finnerty

    finnerty F1 World Champ

    May 18, 2004
    10,341
    #22 finnerty, Nov 3, 2009
    Last edited: Nov 3, 2009
    Sorry to hear that the problem did not have a simple solution. You are wise in sending the pump out for a thorough going over --- sounds like the pump may indeed be malfunctioning in some manner.

    Two other things...... Are you 100% confident that are using the correct (OEM spec) seals --- not some aftermarket supplier? And, are you 100% confident that are using the correct (OEM spec) PS fluid? The interaction between seal material / lip design and fluid properties can be VERY sensitive in some applications..........best to use the EXACT parts and fluids.
     
  26. F328GTS/GTB

    F328GTS/GTB Formula Junior

    May 3, 2005
    517
    France
    Full Name:
    Denis
    I went quickly through the posts. I have been designing hydraulic steering gears from years in a big company. Unfortunately, we don't deliver parts to Ferrari...

    - Leaking oil seals, as you mentionned, is very rare on "modern" cars.
    At first, I thought of a boots damage -which are only filled with AIR, not oil-, which will cause damages to the rack (mainly corrosion, dirts, ...). This will then result to oil seal lip wear and then leakage. This can be easily checked by inspection of the rack diameter roughness and oil seal inspection. If you didn't notice any damage, this should not be this.
    - I would be surprised of increased pressure due to limitor or other. All suppliers seals are validated till 130/140 bar (14 MPa). I would be surprised that the pressure inside the system is higher than 100 bar. The pressure should be very high to damage the seals, which should lead to less steering wheel torque. Did you notice any change in the steering wheel ("lighter" in parking end lock ?).
    - Be careful about oil pollution, that can damage all hydraulic components a lot.
    - There should be two tightnesses on the hydraulic cylinder : left side : oil seal; right side : oil seal + oring. If you have leakage from both sides, it means that oil leak through the seals.
    - As already posted : oil, oil seals are factory recommanded, not "aftermarket" ?

    - I think the supplier of the rack of 456 is ZF, known to be a good supplier. Do you have pictures of your steering gear ?


    Based on my experience in steering gear design of many years, the only rack seals 'big" leakage I see resulted from poor oil seal design. For all other development, rack is tight, maximum 1 or 2 cc at the end of severe endurance tests, including cold temperature. (some seals have a bad behaviour in very cold conditions, which shouldn't be the cause of your issue).

    Keep us posted !
     
  27. SonomaRik

    SonomaRik F1 Veteran
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    Dec 15, 2006
    6,715
    Sonoma, CA
    #24 SonomaRik, Nov 3, 2009
    Last edited: Nov 3, 2009
    a bit off track, but in there anyway: Check your motor mounts too, as it can cause steering failure/problems for the 456. Not saying it's your problem but worthy of checking.
     
  28. 456 koirra

    456 koirra Karting

    Aug 18, 2005
    95
    Finland
    Thanks again for the replies!

    Yes! the steering did feel very light! What does this mean then? too much pressure? I recall that on the pump it was said that it was rated to 90 bar.

    On the manual Dexron II oil is recommended, I've tried a couple of different ones. Last tankfuls have been Mobil ATF 220.
    The seals are indeed aftermarket. I've been told that Ferrari does not repair steering racks but just replaces them and I didn't even think of asking if they'd supply me some seals.

    Yes, the rack is made by ZF. But no, I do not have any pics. Didn't take any, even when I had it open the second time. How stupid! :eek:


    As soon as I hear from the pump specialist I will go to the car (located further away), double check the Motor mounts.

    Anything special I should think of before installing the pump?

    Will keep you posted!
     

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