Suspension Guru's - Please Help
05-05-2011, 05:30 AM
#11
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If the compressor had failed, by now there would be no residual pressure so it must be OK, and by the same token, if it were failing it would either overheat or be noisy and rub for too long.
My guess is a controller fault, possibly caused by too low voltage - the OP does not mention why he has enough concern over the battery to be replacing it as a matter of course.
My guess is a controller fault, possibly caused by too low voltage - the OP does not mention why he has enough concern over the battery to be replacing it as a matter of course.
As an aside, the suspension was soft immediately after replacing the batt but within 5 mins of driving, it hardened up again. (Not rock hard though)??????
05-05-2011, 11:57 PM
#13
AudiWorld Super User
There are two separate issues to deal with.
The ride height is governed by the air springs and is directly proportionate to the air pressure applied to each spring. The damping is controlled by means of adjusting the resistance to fluid flow internaly in the dampers inside the air spring units.
If the ride height and control is working properly and the car does not drop if left in 'jack mode' overnight, then the air side of things is working normally. If the ride stiffens up then goes soft unpredictably then it is the damping control which is not working properly.
I am not sure if both damping and ride height are both set from the same module but they are capable of being controlled separately. If you have the car set in comfort mode it does not lower as much or increase damping rates as much, but it still does lower the car at higher speeds.
I think there is an Audi self studey PDF on the suspension which is worth looking for - there was a link to a whole load of self study docs here a while ago. The only way to find this fault is to understand the system and work from what it should be doing v/s what it is doing.
If things have improved with the new battery fitted then at least that is some preogress. Does the car have any water leaks and has the weather been very wet there - I guess you're now into Autumn now as we are having the warmest, dryest spring on record here in Blighty?
Do the windows steam up when the car is parked in the sun and it then gets cooler (other than for reasons only you and your good lady should know about)?
The ride height is governed by the air springs and is directly proportionate to the air pressure applied to each spring. The damping is controlled by means of adjusting the resistance to fluid flow internaly in the dampers inside the air spring units.
If the ride height and control is working properly and the car does not drop if left in 'jack mode' overnight, then the air side of things is working normally. If the ride stiffens up then goes soft unpredictably then it is the damping control which is not working properly.
I am not sure if both damping and ride height are both set from the same module but they are capable of being controlled separately. If you have the car set in comfort mode it does not lower as much or increase damping rates as much, but it still does lower the car at higher speeds.
I think there is an Audi self studey PDF on the suspension which is worth looking for - there was a link to a whole load of self study docs here a while ago. The only way to find this fault is to understand the system and work from what it should be doing v/s what it is doing.
If things have improved with the new battery fitted then at least that is some preogress. Does the car have any water leaks and has the weather been very wet there - I guess you're now into Autumn now as we are having the warmest, dryest spring on record here in Blighty?
Do the windows steam up when the car is parked in the sun and it then gets cooler (other than for reasons only you and your good lady should know about)?
05-06-2011, 02:07 AM
#14
AudiWorld Member
Suspension Problem
I changed the battery as it was failing more & more often to the point that systems were shutting down. That's fixed now with new batt but as explained above, still got susp issue. Are you suggesting that it's now damaged though?
As an aside, the suspension was soft immediately after replacing the batt but within 5 mins of driving, it hardened up again. (Not rock hard though)??????
As an aside, the suspension was soft immediately after replacing the batt but within 5 mins of driving, it hardened up again. (Not rock hard though)??????
Last edited by A8nightmare; 05-06-2011 at 02:16 AM.
05-06-2011, 08:28 AM
#15
AudiWorld Super User
If the ride height and control is working properly and the car does not drop if left in 'jack mode' overnight, then the air side of things is working normally.
If things have improved with the new battery fitted then at least that is some progress.
05-06-2011, 01:37 PM
#16
AudiWorld Super User
As I said, the ride height IS controlled by the air springs and is directly proportionate to the pressure applied to them.
As far as I can see if the cars stays level when left for an extended period in 'jack' mode, then at least the air springs as is the pipework up to the point of the valves which close to hold the pressure - I guess these are at the distribution unit?
It is a difficult one but I suspect a control issue rather than an actual hardware fault.
As far as I can see if the cars stays level when left for an extended period in 'jack' mode, then at least the air springs as is the pipework up to the point of the valves which close to hold the pressure - I guess these are at the distribution unit?
It is a difficult one but I suspect a control issue rather than an actual hardware fault.
05-06-2011, 05:03 PM
#17
AudiWorld Super User
On the other hand if you load more weight to the car you need higher pressure to create more force to carry that extra weight.
So, pressure proportionate to the load while spring volume is constant and hight constant. Volume proportionate to the hight while pressure is constant and load constant.
05-06-2011, 07:19 PM
#18
Readings
without the actual values/readings from the car is very hard to figure this, all you will get is many different suggestions,
when i said shock leakage I din't mean the spring, I meant the actual shock/damper.
they leak from time to time like a regular shock contaminating the system.
opposite to other brands Audi recirculates the air thru the system and that is the reason when something fails affects the entire pneumatic circuit.
the compressor should be at 14 bar when new but not less than 10 to keep things up and be able to have damping control.
when i said shock leakage I din't mean the spring, I meant the actual shock/damper.
they leak from time to time like a regular shock contaminating the system.
opposite to other brands Audi recirculates the air thru the system and that is the reason when something fails affects the entire pneumatic circuit.
the compressor should be at 14 bar when new but not less than 10 to keep things up and be able to have damping control.
05-06-2011, 07:24 PM
#19
AudiWorld Super User
without the actual values/readings from the car is very hard to figure this, all you will get is many different suggestions,
when i said shock leakage I din't mean the spring, I meant the actual shock/damper.
they leak from time to time like a regular shock contaminating the system.
opposite to other brands Audi recirculates the air thru the system and that is the reason when something fails affects the entire pneumatic circuit.
the compressor should be at 14 bar when new but not less than 10 to keep things up and be able to have damping control.
when i said shock leakage I din't mean the spring, I meant the actual shock/damper.
they leak from time to time like a regular shock contaminating the system.
opposite to other brands Audi recirculates the air thru the system and that is the reason when something fails affects the entire pneumatic circuit.
the compressor should be at 14 bar when new but not less than 10 to keep things up and be able to have damping control.
05-06-2011, 11:43 PM
#20
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Hi guys,
Sorry, been busy pulling the inner guard out to have a look around. I'm not mechincally inclined so it's taken me ages! (Also nursing a broken back so being on a cold concrete floor doesn't help.)
I had a good read of the SSP292 and learnt a lot.
It appears that the car sinks at the front in jacking mode.
I managed to find the compressor and checked the airlines from the struts to the solonoid valve block (except where the RHS runs behind the engine to the sol valve block). They 'look' OK. I'd like to pull the lines off and check pressures etc, but I simply do not how to.
Anyway, a couple of responses below:
Edd - the compressor runs. I've managed to record the noise to see if you guys think that it's normal. I took the covers off everything so it's fairly noisy and I noticed that it's vibrating badly. I can see it moving around "all over the shop" when it's operating. I note that it doesn't turn off either until the ignition is killed. I turned the ignition on, the comp runs and runs and runs and now I get no lift at all... Yellow and green flash for about 2-3 mins then yellow stays on and green continues to flash. (Not worried about the green though). My indi has logged the faults and I'm waiting for him to email them to me.
I rolled down my street and the suspension is rock hard now. I suspect it's failed completely now. Intereestingly though, all the suspensions options are available except 'lift' on the MMI...
This intrigues me. Can this have a role in the xenon lighting level also? I noticed that the lights are not throwing the correct light?
No moisture in the car Edd, windows are fine. (As for the wifey, well, I wouldn't want to the leather soiled! 
)
I read the SSP292 also - great document, but it doesn't give the faults and recommended places to look for each component and what they should be doing. i.e. fault finding tips or something.
Given my comments at the top of this post - does that now help you with the damping versus control query?
A8nightmare - given my comments above - would this still apply?
mishar - see above comments - dropping in jacking mode. I've got a feeling though the that level sensing error is being thrown due to the ride height being so low due to the failure. So, essesntially no change since the new batt.
s4master - I note your comment on 14bar. Is that the compressor pressure? And therefore that should be read at each strut? For example, when the indi ran the individual strut checks to lift / lower, the VagCom stated that each strut was at 6.84bar.... This suggests that it could be the sol valve block, the controller or the compressor being at fault. And, given the drop in jacking mode, I'm seriously confused...
I could not get the pump temp though.
Ah geez - I wish I had the VagCom myself... By the time I order one and get it shipped to Australia - I would have done myself in!
It's been two days already without driving her and I hate it!
Sorry, been busy pulling the inner guard out to have a look around. I'm not mechincally inclined so it's taken me ages! (Also nursing a broken back so being on a cold concrete floor doesn't help.)
I had a good read of the SSP292 and learnt a lot.
It appears that the car sinks at the front in jacking mode.
I managed to find the compressor and checked the airlines from the struts to the solonoid valve block (except where the RHS runs behind the engine to the sol valve block). They 'look' OK. I'd like to pull the lines off and check pressures etc, but I simply do not how to.
Anyway, a couple of responses below:
I rolled down my street and the suspension is rock hard now. I suspect it's failed completely now. Intereestingly though, all the suspensions options are available except 'lift' on the MMI...
This intrigues me. Can this have a role in the xenon lighting level also? I noticed that the lights are not throwing the correct light?
There are two separate issues to deal with.
The ride height is governed by the air springs and is directly proportionate to the air pressure applied to each spring. The damping is controlled by means of adjusting the resistance to fluid flow internaly in the dampers inside the air spring units.
If the ride height and control is working properly and the car does not drop if left in 'jack mode' overnight, then the air side of things is working normally. If the ride stiffens up then goes soft unpredictably then it is the damping control which is not working properly.
I am not sure if both damping and ride height are both set from the same module but they are capable of being controlled separately. If you have the car set in comfort mode it does not lower as much or increase damping rates as much, but it still does lower the car at higher speeds.
I think there is an Audi self studey PDF on the suspension which is worth looking for - there was a link to a whole load of self study docs here a while ago. The only way to find this fault is to understand the system and work from what it should be doing v/s what it is doing.
If things have improved with the new battery fitted then at least that is some preogress. Does the car have any water leaks and has the weather been very wet there - I guess you're now into Autumn now as we are having the warmest, dryest spring on record here in Blighty?
Do the windows steam up when the car is parked in the sun and it then gets cooler (other than for reasons only you and your good lady should know about)?
The ride height is governed by the air springs and is directly proportionate to the air pressure applied to each spring. The damping is controlled by means of adjusting the resistance to fluid flow internaly in the dampers inside the air spring units.
If the ride height and control is working properly and the car does not drop if left in 'jack mode' overnight, then the air side of things is working normally. If the ride stiffens up then goes soft unpredictably then it is the damping control which is not working properly.
I am not sure if both damping and ride height are both set from the same module but they are capable of being controlled separately. If you have the car set in comfort mode it does not lower as much or increase damping rates as much, but it still does lower the car at higher speeds.
I think there is an Audi self studey PDF on the suspension which is worth looking for - there was a link to a whole load of self study docs here a while ago. The only way to find this fault is to understand the system and work from what it should be doing v/s what it is doing.
If things have improved with the new battery fitted then at least that is some preogress. Does the car have any water leaks and has the weather been very wet there - I guess you're now into Autumn now as we are having the warmest, dryest spring on record here in Blighty?
Do the windows steam up when the car is parked in the sun and it then gets cooler (other than for reasons only you and your good lady should know about)?
)I read the SSP292 also - great document, but it doesn't give the faults and recommended places to look for each component and what they should be doing. i.e. fault finding tips or something.
Given my comments at the top of this post - does that now help you with the damping versus control query?
If your compressor is turns out to be good, you may have a stuck or sticky check valve in the air distrubution manifold. This would dump the air not allowing anything to inflate at times explaining why the compressor runs , but you don't hear any leaking. That would further explain some of the odd symptoms you are having. For example the valve may be partially stuck or not seating properly...hence the suspension sagging and not hardening up all the way. Unfortunately moisture or water can get into the valve body and makes them stick. It is repairable.
Not really. The drive height is proportionate to amount of air pumped into springs. Pressure is constant, just enough to oppose car weight, which is constant too. When we load the car compressor pumps springs a bit more to compensate extra weight.
That part we don't know. I've told him earlier to do so but there was not response.
If there is a faulty height sensor it might work a bit better with a bit higher voltage.
That part we don't know. I've told him earlier to do so but there was not response.
If there is a faulty height sensor it might work a bit better with a bit higher voltage.
without the actual values/readings from the car is very hard to figure this, all you will get is many different suggestions,
when i said shock leakage I din't mean the spring, I meant the actual shock/damper.
they leak from time to time like a regular shock contaminating the system.
opposite to other brands Audi recirculates the air thru the system and that is the reason when something fails affects the entire pneumatic circuit.
the compressor should be at 14 bar when new but not less than 10 to keep things up and be able to have damping control.
when i said shock leakage I din't mean the spring, I meant the actual shock/damper.
they leak from time to time like a regular shock contaminating the system.
opposite to other brands Audi recirculates the air thru the system and that is the reason when something fails affects the entire pneumatic circuit.
the compressor should be at 14 bar when new but not less than 10 to keep things up and be able to have damping control.
I could not get the pump temp though.
Ah geez - I wish I had the VagCom myself... By the time I order one and get it shipped to Australia - I would have done myself in!
It's been two days already without driving her and I hate it!