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#21
11-02-2009, 02:55 AM
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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! 
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#22
11-03-2009, 02:08 PM
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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. Last edited by finnerty; 11-03-2009 at 02:12 PM.
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#23
11-03-2009, 03:04 PM
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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 !
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#24
11-03-2009, 03:31 PM
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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.
Last edited by SonomaRik; 11-03-2009 at 03:48 PM.
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#25
11-05-2009, 04:59 AM
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Thanks again for the replies!
Quote:
Quote:
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. Quote:
 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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#26
11-05-2009, 03:29 PM
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Quote:
90 bar is a normal pressure for steering system. On some system, pressure is increased till 120 bars, but on the 456, I don't know. 90 bar seems Ok for me. I suppose the pressure limitor is located on the pump, which is normal. What is important is that IF you notice a reduction of the steering wheel torque at end lock, it means that you had more assistance in the rack cylinder, which is due to more pressure inside the system. (Reason ?). ATF 220 is valid oil for steering system, even if not the best one (at cold temperature, the viscosity is very high, which lead to change of steering wheel torque, but you shouldn't use your Ferrari at very cold conditions ...). What do you mean by "i've tried a couple of different ones" ? Is it requested in the maintenance book to change the oil regularly ????? Steering oil can be used for many many years without any change. It is not like braking fluid with water charging inside oil. Normally, even aftermarket seals should be compatible with ATF oils. If all dimensions, correct way of assembling are good, it should work and be tight. But be careful, how did you choose aftermarket seals : did you know the exact dimensions of ZF seals and seal material ? Concerning material, HNBR or VITON should be used. Never use NBR material which will have a bad behaviour in severe temperature environnement. Still interested to have pics of your racks (close pics of the rack bar, seals, and general view). Next time !
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#27
11-06-2009, 08:08 AM
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Quote:
If there turns out to be a problem with the pump, I guess it makes sense to first try the system with the present seals as the rack is in place but if I have to take it out I will definately take pictures of it! I will check the material of the seals. And get back as soon as I have some news. from the shop where the pump is or from where ever! Thanks for your effort!
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#28
11-08-2009, 07:33 AM
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for your info, I send you an extract of a hydraulic steering gear drawing. May be your ZF gear is not exactly the same design, but more or less, all steering gears are in the same "easy" structure.
Tightness is done by the two oil seals around the rack (n°4 and 13). The oring n°12 makes tightness between rack bush and rack housing.
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