Any power steering gurus here?
Discussion
Hi folks,
I'm after some advice (or a proper power steering specialist) in relation to a problem I'm having with the PAS on our S-Max.
It's an '07 2.0 TDCI which is the only S-Max fitted with electro-hydraulic PAS.
The PAS seems to become ineffective particularly when weather is cold and has been intermittently problematic for over 12 months. The symptoms are that the steering will feel initially unassisted, then the assistance will cut in. As the situation worsens it can end up feeling entirely unassisted, though it will cut back in intermittently. It doesn't always happen, but is worsening of late. There are no leaks, the fluid level doesn't drop and there is no play in the rack. I can hear the pump running, and the pump revs increasing as demand increases when load is applied to the steering column.
Back in March I read somewhere that in order to bleed the rack properly it was necessary to remove the track rod ends to enable the rack to get to the end of its travel. I did this and was delighted that it cured the problem completely - for a while. At the beginning of the month (cold weather?) the symptoms returned. I did some more homework and saw that some Ford dealers are apparently "fixing" this by replacing the reservoir as there is a filter in the bottom which may get blocked. I drained the system, cleaned out the reservoir thoroughly, dropped the track rod ends and re-bled the system again with fresh, Ford fluid. It then worked perfectly until this morning when the symptoms have returned.
I'm a bit stuck now, I tend to avoid main dealers, everything I have seen on the net about this problem suggests that main dealers just want to put a rack or a pump on it (or both). However, I know that the pump CAN provide sufficient pressure and that the rack CAN work effectively - it just doesn't seem to do so for very long.
Does anyone have any ideas to help me further at this stage or contacts for a decent power steering specialist (rather than just someone who will rebuild the rack) - preferably in the Midlands area.
I'm after some advice (or a proper power steering specialist) in relation to a problem I'm having with the PAS on our S-Max.
It's an '07 2.0 TDCI which is the only S-Max fitted with electro-hydraulic PAS.
The PAS seems to become ineffective particularly when weather is cold and has been intermittently problematic for over 12 months. The symptoms are that the steering will feel initially unassisted, then the assistance will cut in. As the situation worsens it can end up feeling entirely unassisted, though it will cut back in intermittently. It doesn't always happen, but is worsening of late. There are no leaks, the fluid level doesn't drop and there is no play in the rack. I can hear the pump running, and the pump revs increasing as demand increases when load is applied to the steering column.
Back in March I read somewhere that in order to bleed the rack properly it was necessary to remove the track rod ends to enable the rack to get to the end of its travel. I did this and was delighted that it cured the problem completely - for a while. At the beginning of the month (cold weather?) the symptoms returned. I did some more homework and saw that some Ford dealers are apparently "fixing" this by replacing the reservoir as there is a filter in the bottom which may get blocked. I drained the system, cleaned out the reservoir thoroughly, dropped the track rod ends and re-bled the system again with fresh, Ford fluid. It then worked perfectly until this morning when the symptoms have returned.
I'm a bit stuck now, I tend to avoid main dealers, everything I have seen on the net about this problem suggests that main dealers just want to put a rack or a pump on it (or both). However, I know that the pump CAN provide sufficient pressure and that the rack CAN work effectively - it just doesn't seem to do so for very long.
Does anyone have any ideas to help me further at this stage or contacts for a decent power steering specialist (rather than just someone who will rebuild the rack) - preferably in the Midlands area.
The pump sends out a "status" message over the CAN bus, this includes the pump "Load". You need to determine if the issue is a "lack of electrical power" (i.e. the electric motor simply isn't turning the hydraulic pump fast enough to assist) or a "lack of hydraulic pressure/flow" (i.e the hydraulic pump IS being spun correctely, but cannot for some reason supply sufficient oil flow/pressure to assist).
If you log the pump status message you will at least be able to see if it "thinks" it is fully assisting.
There is also a spring loaded pressure relief valve in the pump body that could be jamming open??
If you log the pump status message you will at least be able to see if it "thinks" it is fully assisting.
There is also a spring loaded pressure relief valve in the pump body that could be jamming open??
Thanks for the reply.
I've had the fault codes read and nothing was logged in relation to the PAS. I can also hear the pump spinning up when toque is applied at the steering wheel, so I believe that the correct signal is arriving at the pump. The fact that the system also seems to work for some time after it's bled makes me think that the pumps is able to supply sufficient pressure.
I get the impression that the problem is related to the hydraulic side - is it possible for it to suck air without leaking fluid, or possibly be related to the valve that has to open when torque is applied? I'd be interested to know how I can check the pressure relief valve - or whether I just need to get the unit reconditioned / replaced.
I could really do with finding a specialist who can look at the whole thing for me rather than adopting the main dealer approach of just replacing major components at the customer's expense until you hit upon the right one... If anyone can make a recommendation I'm all ears
I've had the fault codes read and nothing was logged in relation to the PAS. I can also hear the pump spinning up when toque is applied at the steering wheel, so I believe that the correct signal is arriving at the pump. The fact that the system also seems to work for some time after it's bled makes me think that the pumps is able to supply sufficient pressure.
I get the impression that the problem is related to the hydraulic side - is it possible for it to suck air without leaking fluid, or possibly be related to the valve that has to open when torque is applied? I'd be interested to know how I can check the pressure relief valve - or whether I just need to get the unit reconditioned / replaced.
I could really do with finding a specialist who can look at the whole thing for me rather than adopting the main dealer approach of just replacing major components at the customer's expense until you hit upon the right one... If anyone can make a recommendation I'm all ears
Sounds like the valve in the steering rack is sticking.
The pump speed is generally controlled from a sensor in the steering column (there are other methods), so as you turn the steering wheel the speed increases to provide flow.
The pressure and resultant assistance is regulated from a valve in the steering rack, if the valve is stuck or sticking then you will get none or little assistance, the pump speed can increase, this will get more flow, but if the valve is closed none of it will go into the rack.
The pump speed is generally controlled from a sensor in the steering column (there are other methods), so as you turn the steering wheel the speed increases to provide flow.
The pressure and resultant assistance is regulated from a valve in the steering rack, if the valve is stuck or sticking then you will get none or little assistance, the pump speed can increase, this will get more flow, but if the valve is closed none of it will go into the rack.
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