Air Suspension data needed/Help, please
11-29-2018, 10:03 AM
#1
AudiWorld Member
Thread Starter
Air Suspension data needed/Help, please
I’ll start out saying that this system is more complex it seems than the 04 Allroad I recently sold. Only had the D3 a month now. I have not found info that answers my questions specifically for what my data should look like after searching and searching.
Previously I ran VCDS to find that I was getting intermittent Overheat codes and G291 issues. See below. I was also able to see that I never had more than 7 BAR when the compressor was running. I have rebuilt the compressor and now see up to 15.3 BAR.
Previous codes, never at the same time. Only Code since rebuild is the 01772.:
01772 – Signal from Level Control Pressure Sensor (G291)
01400 - Suspension Level Control 002 - Lower Limit Exceeded (1 time)
01577 - Turn-Off due to Over-Temp 001 - Upper Limit Exceeded – Intermittent
I have done the tape test overnight. Appeared that all 4 corners came down slightly the same amount. This leads me to think I have a leak at the valve block? I have also been driving in Dynamic mode 100% of the time the last week or so. Every time I get in the car after a longer drive the Green Suspension Extreme low level light comes on at start up. This appears to be telling me I am lower than I should be from the study guide, but is not an actual malfunction, study guide does not really clarify this for me.
Attached is a log from my drive this morning. What I noticed is that the compressor ran a bit more than I expected as I was getting to the highway. Once on the highway I don’t recall seeing it turn on more than 1 time.
Other things I noticed in the logs were:
Plan of attack is to look for leaks and make sure all connections to the valve block are snug and same thing at all 4 connections to springs.
Previously I ran VCDS to find that I was getting intermittent Overheat codes and G291 issues. See below. I was also able to see that I never had more than 7 BAR when the compressor was running. I have rebuilt the compressor and now see up to 15.3 BAR.
Previous codes, never at the same time. Only Code since rebuild is the 01772.:
01772 – Signal from Level Control Pressure Sensor (G291)
01400 - Suspension Level Control 002 - Lower Limit Exceeded (1 time)
01577 - Turn-Off due to Over-Temp 001 - Upper Limit Exceeded – Intermittent
I have done the tape test overnight. Appeared that all 4 corners came down slightly the same amount. This leads me to think I have a leak at the valve block? I have also been driving in Dynamic mode 100% of the time the last week or so. Every time I get in the car after a longer drive the Green Suspension Extreme low level light comes on at start up. This appears to be telling me I am lower than I should be from the study guide, but is not an actual malfunction, study guide does not really clarify this for me.
Attached is a log from my drive this morning. What I noticed is that the compressor ran a bit more than I expected as I was getting to the highway. Once on the highway I don’t recall seeing it turn on more than 1 time.
Other things I noticed in the logs were:
- Compressor on and pressure to 12-15 BAR then turns off and pressure immediately goes to approx 2-4 BAR. Odd
- When on the highway the pressure seemed to climb with no compressor turn on. Went from 3-4 to 7.49 to 9.11 then dropped a bit, due to dynamic lowering?
- Front right is always a bit low. Will try calibration.
Plan of attack is to look for leaks and make sure all connections to the valve block are snug and same thing at all 4 connections to springs.
- What pressure should the system hold when driving after the compressor kicks off?
- Should I replace the Relay? Will order one since they are cheap and I need a few things anyway.
- Is the Allroad valve block the same as the d3 A8 ( I have a spare)? Given the G291 is part of the valve block might need to replace that.
- What is the O-ring size for the connectors to the valve block?
- I attempted to do the calibration , in VCDS adaptation this afternoon. Took all the measurements but no changes. Front right still is lower than the rest. Did it 4 times. 01 value, test save, 02 same, 03 same , 04 same , 05 - 1 test save. Then it re-levels no change.
Last edited by cu52; 11-29-2018 at 12:10 PM.
11-30-2018, 08:46 AM
#2
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1. The car will lower slightly overnight. Maybe 1/2 inch all around. As the air cools, the pressure drops a bit. Usually if you have a shock leaking, it will drop a lot more than that. Try letting is sit a bit longer to see if it continues to drop.
2. The compressor does run quite a bit. Many times you don't know it, because you can't hear it. I logged mine once and I think it cycled about every 10 minutes during highway ride. Also when hitting 75 mph, the car lowers even more than dynamic. So when slowing, it raise a bit. I think it's something like an additional 1/2". So if driving in normal / comfort, it raising / lowering close to 1.5".
3. In Dynamic mode, the green light will always come on when starting the car. This is to remind you that the car is lowered - lower than "normal".
4. When driving the air will heat up due to the constant compression of the shocks as they cycle up and down.
5. The suspension operates around 15 - 16 bar when driving. So you are talking 220 - 230 PSI. .....It takes quite a bit of work to maintain this.
2. The compressor does run quite a bit. Many times you don't know it, because you can't hear it. I logged mine once and I think it cycled about every 10 minutes during highway ride. Also when hitting 75 mph, the car lowers even more than dynamic. So when slowing, it raise a bit. I think it's something like an additional 1/2". So if driving in normal / comfort, it raising / lowering close to 1.5".
3. In Dynamic mode, the green light will always come on when starting the car. This is to remind you that the car is lowered - lower than "normal".
4. When driving the air will heat up due to the constant compression of the shocks as they cycle up and down.
5. The suspension operates around 15 - 16 bar when driving. So you are talking 220 - 230 PSI. .....It takes quite a bit of work to maintain this.
11-30-2018, 08:52 AM
#3
AudiWorld Member
Thread Starter
1. The car will lower slightly overnight. Maybe 1/2 inch all around. As the air cools, the pressure drops a bit. Usually if you have a shock leaking, it will drop a lot more than that. Try letting is sit a bit longer to see if it continues to drop.
2. The compressor does run quite a bit. Many times you don't know it, because you can't hear it. I logged mine once and I think it cycled about every 10 minutes during highway ride. Also when hitting 75 mph, the car lowers even more than dynamic. So when slowing, it raise a bit. I think it's something like an additional 1/2". So if driving in normal / comfort, it raising / lowering close to 1.5".
3. In Dynamic mode, the green light will always come on when starting the car. This is to remind you that the car is lowered - lower than "normal".
4. When driving the air will heat up due to the constant compression of the shocks as they cycle up and down.
5. The suspension operates around 15 - 16 bar when driving. So you are talking 220 - 230 PSI. .....It takes quite a bit of work to maintain this.
2. The compressor does run quite a bit. Many times you don't know it, because you can't hear it. I logged mine once and I think it cycled about every 10 minutes during highway ride. Also when hitting 75 mph, the car lowers even more than dynamic. So when slowing, it raise a bit. I think it's something like an additional 1/2". So if driving in normal / comfort, it raising / lowering close to 1.5".
3. In Dynamic mode, the green light will always come on when starting the car. This is to remind you that the car is lowered - lower than "normal".
4. When driving the air will heat up due to the constant compression of the shocks as they cycle up and down.
5. The suspension operates around 15 - 16 bar when driving. So you are talking 220 - 230 PSI. .....It takes quite a bit of work to maintain this.
2 questions I still have:
What is the normal pressure of the system after the compressor stops?
Would a bad valve block be causing the G291 issue? I will try to to clean the connections to make sure that is not the issue first.
11-30-2018, 01:55 PM
#4
AudiWorld Super User
I wouldn't worry so much about the pressure stuff, if the valve block is working ie, G291 is working, the pressure will be automatically good if there's no leak in the system.
About the VCDS reports, if the system leaks, the pump must pump to fill up the tank per valve block requests, get hot and system shut it down - hence the report. The system leaks, the struts lowered level sensor shows low, hence the report. When the system is bad, all parts related to the system will show up as fault. Stop looking at the VCDS and start using troubleshooting techniques from people who've done it. Unless you have all the money to replace everything, and even then, you may not even hit the right tree.
Cheers,
Louis
About the VCDS reports, if the system leaks, the pump must pump to fill up the tank per valve block requests, get hot and system shut it down - hence the report. The system leaks, the struts lowered level sensor shows low, hence the report. When the system is bad, all parts related to the system will show up as fault. Stop looking at the VCDS and start using troubleshooting techniques from people who've done it. Unless you have all the money to replace everything, and even then, you may not even hit the right tree.
Cheers,
Louis
11-30-2018, 02:51 PM
#5
AudiWorld Wiseguy
Don’t over think it. Your symptoms are in line with a slow strut leak.....90% of the time this is the root cause.
Park it up overnight in jacking mode (disables sleep mode auto-level function) and measure each corner height in the morning. This will show which corner is leaking.
Also on the early cars (I think < 06), the green light is on whenever the car is in dynamic or highway lowering mode, as well as when it’s too low. So I wouldn’t worry too much about this coming on, especially as you’ve had it in dynamic mode for the past week.
Park it up overnight in jacking mode (disables sleep mode auto-level function) and measure each corner height in the morning. This will show which corner is leaking.
Also on the early cars (I think < 06), the green light is on whenever the car is in dynamic or highway lowering mode, as well as when it’s too low. So I wouldn’t worry too much about this coming on, especially as you’ve had it in dynamic mode for the past week.
Last edited by dvs_dave; 11-30-2018 at 03:01 PM.
12-03-2018, 09:42 AM
#6
AudiWorld Member
Thread Starter
I wouldn't worry so much about the pressure stuff, if the valve block is working ie, G291 is working, the pressure will be automatically good if there's no leak in the system.
About the VCDS reports, if the system leaks, the pump must pump to fill up the tank per valve block requests, get hot and system shut it down - hence the report. The system leaks, the struts lowered level sensor shows low, hence the report. When the system is bad, all parts related to the system will show up as fault. Stop looking at the VCDS and start using troubleshooting techniques from people who've done it. Unless you have all the money to replace everything, and even then, you may not even hit the right tree.
Cheers,
Louis
About the VCDS reports, if the system leaks, the pump must pump to fill up the tank per valve block requests, get hot and system shut it down - hence the report. The system leaks, the struts lowered level sensor shows low, hence the report. When the system is bad, all parts related to the system will show up as fault. Stop looking at the VCDS and start using troubleshooting techniques from people who've done it. Unless you have all the money to replace everything, and even then, you may not even hit the right tree.
Cheers,
Louis
Don’t over think it. Your symptoms are in line with a slow strut leak.....90% of the time this is the root cause.
Park it up overnight in jacking mode (disables sleep mode auto-level function) and measure each corner height in the morning. This will show which corner is leaking.
Also on the early cars (I think < 06), the green light is on whenever the car is in dynamic or highway lowering mode, as well as when it’s too low. So I wouldn’t worry too much about this coming on, especially as you’ve had it in dynamic mode for the past week.
Park it up overnight in jacking mode (disables sleep mode auto-level function) and measure each corner height in the morning. This will show which corner is leaking.
Also on the early cars (I think < 06), the green light is on whenever the car is in dynamic or highway lowering mode, as well as when it’s too low. So I wouldn’t worry too much about this coming on, especially as you’ve had it in dynamic mode for the past week.
I do appreciate all the responses.
12-03-2018, 05:50 PM
#7
AudiWorld Wiseguy
Remember that the sleep mode auto level function only works whilst there is sufficient air pressure in the accumulator. If there is a slow leak not in a strut, the air pressure in the accumulator will gradually decrease until autolevel will no longer work. It can’t command the compressor to run whilst in sleep mode. Then of course the whole car will sink down equally on all corners.
Also it’s harder to tell which corner it is on an A8 as the roll bars and frame are stiffer than on an allroad, so it will typically be the whole front or rear of the car that sinks down, with the leaky corner only being a little bit lower, so accurate height measurements are important.
Regards other owner data, kind of irrelevant as every car is different and the system has a very wide acceptable performance envelope tolerance before throwing a code. SSP 292 is crucial reading if you want to have any hope of accurately diagnosing a problem with the system.
Also it’s harder to tell which corner it is on an A8 as the roll bars and frame are stiffer than on an allroad, so it will typically be the whole front or rear of the car that sinks down, with the leaky corner only being a little bit lower, so accurate height measurements are important.
Regards other owner data, kind of irrelevant as every car is different and the system has a very wide acceptable performance envelope tolerance before throwing a code. SSP 292 is crucial reading if you want to have any hope of accurately diagnosing a problem with the system.
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12-03-2018, 06:33 PM
#8
AudiWorld Member
Thread Starter
Remember that the sleep mode auto level function only works whilst there is sufficient air pressure in the accumulator. If there is a slow leak not in a strut, the air pressure in the accumulator will gradually decrease until autolevel will no longer work. It can’t command the compressor to run whilst in sleep mode. Then of course the whole car will sink down equally on all corners.
Also it’s harder to tell which corner it is on an A8 as the roll bars and frame are stiffer than on an allroad, so it will typically be the whole front or rear of the car that sinks down, with the leaky corner only being a little bit lower, so accurate height measurements are important.
Regards other owner data, kind of irrelevant as every car is different and the system has a very wide acceptable performance envelope tolerance before throwing a code. SSP 292 is crucial reading if you want to have any hope of accurately diagnosing a problem with the system.
Also it’s harder to tell which corner it is on an A8 as the roll bars and frame are stiffer than on an allroad, so it will typically be the whole front or rear of the car that sinks down, with the leaky corner only being a little bit lower, so accurate height measurements are important.
Regards other owner data, kind of irrelevant as every car is different and the system has a very wide acceptable performance envelope tolerance before throwing a code. SSP 292 is crucial reading if you want to have any hope of accurately diagnosing a problem with the system.
So current data
Initial Measurements. Vehicle is parked out front so the Right side is in the gutter. Front left, Front Right, Rear Left Rear Right
29.75", 28.875", 29.75", 28.875"
Tonight's measurements
29.5, 28.5, 29.5, 28.625
Current Delta
-.25, -.375, -.25, -.25,
FR might be off slighting in measurements. If I start fresh again ill use my Metric tape for more accuracy.
Above it appears to me that I ether have a small leak at a point that all 4 corners are lowering approx the same amount, or possibly a front and rear leak or all 4 shocks are leaking.
For the SSP 292 i have studied it and not sure where the leak point could be. What I have found when reading it is anytime the system exhausts air, it does not move the pressure from suspension into the accumulator it exhausts which is why the compressor has to kick in to fill the system up again. So a few folks say that the compressor should almost never run, but that would assume that the when system drops pressure goes to accumulator not exhausted.
Occasional I do still get the G291 issue.
12-03-2018, 08:29 PM
#9
AudiWorld Wiseguy
Double check FR. The fact it’s sunk more than the others is potentially your where your problem is. Although you really need to have the car parked on a level surface to eliminate any other errors as the difference isn’t huge. Only reason it’s a red flag here is because the other 3 are so consistent.
Garage is preferable to street. A leak is a leak whether it’s 20F or 50F ambient, however street isn’t necessarily level, gutters, dips, etc.
Garage is preferable to street. A leak is a leak whether it’s 20F or 50F ambient, however street isn’t necessarily level, gutters, dips, etc.
12-04-2018, 06:28 AM
#10
AudiWorld Super User
Well, if you leave the car in jack mode when you park it, if it's a strut leak, that corner would drop the most and it should be clear. If the leak is elsewhere in the system, it shouldn't drop anywhere but the compressor would come on immediately up on turning off jack mode.
