Steering boost comes and goes | FerrariChat

Steering boost comes and goes

Discussion in '456/550/575' started by ///Mink, Sep 18, 2015.

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  1. ///Mink

    ///Mink Formula Junior

    Sep 5, 2006
    808
    Fair Oaks, CA
    Full Name:
    Tom Mink
    I have noticed in the last couple of weeks that my steering effort at low speeds (such as during parking maneuvers) has gone up quite a bit. However, sometimes it returns to normal, too. When the effort goes up, there is still power assist, but it's at a much lower level. The fluid level is normal and there are no funny noises from the pump.

    Would you guys suspect a failing PS pump, or perhaps a problem with the steering ECU? I hate to start throwing parts at it randomly. The car is a '98 550, BTW. I have the stock steering ECU.
     
  2. JM35

    JM35 Karting

    Jun 22, 2014
    75
    Texas
    Tom,

    Does the problem happen also at high speed or only when you are a low speed ?

    The ECU can be the issue
    The ECU have a bad contact on the Speed reference connection point
    The ECU have a bad contact at the signal output connector
    The solenoid that control the pressure vs of the signal receive from the ECU can be faulty
    A bad contact at the steering rack Solenoid

    hope this help
     
  3. tazandjan

    tazandjan Three Time F1 World Champ
    Lifetime Rossa Owner

    Jul 19, 2008
    37,985
    Clarksville, Tennessee
    Full Name:
    Terry H Phillips
    Tom- First thing to do is have the fluid replaced and the system bled (done by turning the steering wheel as described in the WSM). See if that fixes the problem before chasing anything more expensive. The power steering fluid should be changed every two years.

    If the hydraulic steering ECU proves to be bad, good time to upgrade to a Maranello Skunkworks FHP steering ECU.
     
  4. ///Mink

    ///Mink Formula Junior

    Sep 5, 2006
    808
    Fair Oaks, CA
    Full Name:
    Tom Mink

    Thanks Terry! Great to see you back around these parts!
     
  5. fatbillybob

    fatbillybob Two Time F1 World Champ
    Consultant Owner

    Aug 10, 2002
    26,292
    socal
    Taz advice is sound. The cars will work fine with the steering ECU pulled. Some owners say the steering effort really climbs and other say it does not. I'm not sure why except many of these racks have been rebuilt at one time or another and that could make a difference. Anyway a clean 10 second way to take the steering ECU out of the picture is just to remove it for testing. IF you get intermittent light heavy steering with the ECU completely out then maybe you do have a problem in the system elsewhere. If you need to know how to change the fluid report back to this thread.
     
  6. 166&456

    166&456 Formula 3

    Jul 13, 2010
    1,723
    Amsterdam
    Probably a bad (cracked) solder joint in the steering ECU.
     
  7. ///Mink

    ///Mink Formula Junior

    Sep 5, 2006
    808
    Fair Oaks, CA
    Full Name:
    Tom Mink
    Revisiting this thread with some new info. Since my original post, I've replaced the supply line, both return lines, and had the pressure hose rebuilt locally. I also replaced the reservoir since it has a filter in it. While I was at it, I also removed the Servotronic torque converter from the rack and cleaned the little screen behind it (it wasn't really dirty). I've also tried popping out the steering ECU when the boost is low and when I do, the boost drops even more, so I doubt the ECU is the issue (though if someone wanted to loan me a stock ECU to test with, that might be interesting).

    So now the system is nice and leak-free but I am still having sporadic boost levels. Often, the boost level is low when the car is cold and goes back to normal once it warms up, but not always.

    So now I think I'm basically down to either a failing PS pump or a bad rack. I think my symptoms point more to a pump. I know the pump is Ferrari-specific, but I think the guts are standard ZF. Not sure if I should try installing a seal kit or farm out the pump rebuild job.

    Thoughts?
     
  8. Cribbj

    Cribbj Formula 3

    Tom, my money would be on the pump - is it making any noise? P/S pumps often make a whining noise when they're going south.

    Many BMW's & Porsches use a similar pump, so their seal kits will work fine if you want to try that as a cheap solution, and there are how to videos on YouTube & elsewhere. I rebuilt mine, then my rack started puking fluid out the right hand seal, so I took both the rack & pump to a local rebuilder and had them both done & tested.
     
  9. tazandjan

    tazandjan Three Time F1 World Champ
    Lifetime Rossa Owner

    Jul 19, 2008
    37,985
    Clarksville, Tennessee
    Full Name:
    Terry H Phillips
    John- Those guys that redid yours sounded really sharp. If I had problems, would be tempted to ship it to them.
     
  10. fatbillybob

    fatbillybob Two Time F1 World Champ
    Consultant Owner

    Aug 10, 2002
    26,292
    socal
    How did you bleed you PS system?
     
  11. ///Mink

    ///Mink Formula Junior

    Sep 5, 2006
    808
    Fair Oaks, CA
    Full Name:
    Tom Mink
    Tell me if I did this wrong, can't recall where I got this procedure.

    1. Filled system.
    2. Engine off, ran steering lock-to-lock 4 or 5 times.
    3. Topped off.
    4. Started engine for 5 seconds
    5. Engine off, ran steering lock-to-lock 4 or 5 times.
    6. Topped off.
    7. Repeated 4 thru 6 3 or 4 times.
    8. Started engine and ran lock-to-lock a few times, topping off as needed.
    9 Test drove, topping off afterward.
     
  12. fatbillybob

    fatbillybob Two Time F1 World Champ
    Consultant Owner

    Aug 10, 2002
    26,292
    socal
    This tells me still air in system if you had to top off.



    IMO the easiest way and way that has worked for me 100% of the time including on the 550 is to put the front end up on jack stands just to get pressure off the wheels. Top up reservoir. Engine off run lock to lock about 10 times periodically check reservoir level. Start car and use the power steering pump to pump fluid and bleed by going lock to lock about 6 times. Then check fluid level and add if needed. Engine running go lock to lock about 4 times. When you get to lock I hold it there a second or so. Check fluid is at same level. If at same level you are done. If not top up and with engine on run a few more cycles lock to lock and check level again. Once the lock to lock exercise no longer drops the fluid level you are bled out. That bleeds the system from my experience.
     
  13. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    33,736
    Austin TX
    Full Name:
    Brian Crall
    I have had a number of cases of a total or inconsistent failure of the signal to the speed sensitive steering unit. I have never heard of a hydraulic problem causing it.

    That signal goes to several components and I have had to address that exact problem on other cars. It is a variable voltage signal and easy to measure but the circuit goes all over the car. With jumper wires attach a VOM to the plug at the rack and drive around. The voltage signal is proportional with speed but has an upper limit of 5 or 7 volts.
     
  14. ///Mink

    ///Mink Formula Junior

    Sep 5, 2006
    808
    Fair Oaks, CA
    Full Name:
    Tom Mink
    Thanks Brian. I will give that a try this weekend and see what I come up with.
     
  15. ///Mink

    ///Mink Formula Junior

    Sep 5, 2006
    808
    Fair Oaks, CA
    Full Name:
    Tom Mink
    #15 ///Mink, Apr 23, 2016
    Last edited by a moderator: Sep 7, 2017
    Finally resurrecting this thread with a solution! I took Brian's advice above and measured the voltage at the rack at various speeds. It varied between 4 and 8 volts depending on speed and was very consistent. This led me to read up on how servotronic steering works and I decided to look at the Servotronic torque converter on the rack. My research found the part number on it to be the same as many 1990s BMWs. I replaced it and et voilà, I have power steering again!

    The BMW part number for the converter is 32411134770 and I found it online for $165. I will update the parts interchange thread with this info as well. Hooray!
    Image Unavailable, Please Login
     
  16. tazandjan

    tazandjan Three Time F1 World Champ
    Lifetime Rossa Owner

    Jul 19, 2008
    37,985
    Clarksville, Tennessee
    Full Name:
    Terry H Phillips
    Tom- Good info, thanks.
     
  17. MogulBoy

    MogulBoy Formula Junior

    Sep 23, 2004
    969
    Devon
    I should probably brush up on the basics as I know very little about how hydraulic power steering systems work but I see that there is a pump that is driven by an auxiliary belt and that is the source of hydraulic pressure to the system (at all times, e.g. from idle speed right up to the redline).

    One way or another, the available pressure is then regulated so that the rack is fed with just the right amount of power at all engine speeds and thanks to the Servotronic valve, reduced levels of power can be metered out based on the vehicle's increasing speed.

    This all sounds rather complicated as clearly when parking, revs will be low but we need the most assistance. Conversely, when driving fast revs might be high but we might need the least assistance etc....

    Perhaps the Servotronic valve is designed to fail in the low assistance mode?

    e.g. the pump may be capable of providing all of the hydraulic pressure that could ever be asked of it but the Servotronic device in failure mode has the effect of releasing the pressure and the lowest level (possibly nil) of hydraulic assistance is delivered to the rack?
     
  18. Rifledriver

    Rifledriver Three Time F1 World Champ

    Apr 29, 2004
    33,736
    Austin TX
    Full Name:
    Brian Crall
    I can't follow your post.


    The pump has a regulator valve built in and is designed to supply all the pressure required at idle. But it is dumb. It only regulates maximum pressure. The servotronic system senses car speed and is designed to supply the greatest pressure to the rack at low speeds and decrease pressure at higher speeds.


    Designed to fail? It is not designed to fail.
     
    F456M likes this.

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