DIY Air Spring Replacement FAQ
#1
03-25-2010, 01:46 PM
DIY Air Spring Replacement FAQ
I have been following the several threads related to air suspension operation and failure modes and learned a lot. The thing that eludes me:
Is front air spring replacement a job for the mid level home mechanic - given that the dealer will have to run the diagnostic system for set up and ride height?
The JTIS procedure seems straight foward and within my capabilities but there may be a lot in between the lines that could bite me.
Has anybody here done it at home and what say you JagTechs?
Is front air spring replacement a job for the mid level home mechanic - given that the dealer will have to run the diagnostic system for set up and ride height?
The JTIS procedure seems straight foward and within my capabilities but there may be a lot in between the lines that could bite me.
Has anybody here done it at home and what say you JagTechs?
Top Answer
03-31-2010, 05:58 PM
Tarheal,
I've been hesitating answering this because it can become complex and unorthadox without a WDS, or whatever they're calling it these days.
You can pull off the air spring change without reprogrmming the ASM. You have to deviate from the JTIS though. First, you have to understand the basic operating modes and strategies of the AS system. To begin, the ASM will need to be calibrated (suspension height set) only if:
Any height sensor is removed, then reinstalled
The ASM is replaced
or a height sensor is replaced.
While the ASM is active and powered up.
So, you don't want to do any of these, even though JTIS says to remove the height sensor. The ASM is using non-volatile memory to "remember" the inputs of all sensors when it is in certain modes, or when the battery is disconnected. So, you need to outsmart it and create that situation while you are R/Ring the air spring and when the ASM wakes back up.
Briefly, there are five modes the ASM takes depending on "activity". The modes are:
Sleep mode
Preliminary mode
Post mode
Stance mode
Drive mode
You'll be focused on one of these - sleep mode. The ASM goes into sleep mode 30 minutes after the ignition is switched off and the last door or trunk activity is detected. The entire air suspension system shuts down during this time (enters sleep mode) and, if the car is not used, wakes up on a 24 hour clock to check height. At 24 hour intervals, the ASM makes adjustments in height by measuring the lowest sensor and adjusting dwonward so the suspension is even.
Basically, you want to catch the system before sleep mode. You're going to do that by positioning the vehicle where you will work on it, get it raised off the ground and suspended, then disconnect the battery before sleep mode (sooner than 30 minutes after shutting the engine down). By doing this, the ASM will store its inputs from the height sensors with the suspension fully extended. In essence, you're going to perform the surgery on the air springs while the ASM is anesthetized thinking the suspension is in the full extended position. That is what it is going to remember when it wakes up. If it doesn't see that, you'll need to recalibrate the ASM.
Follow most of the JTIS steps now - depressurize the springs, you can use a floor jack to take weight off the airspring, etc., not removing the height sensors. Replace the air springs, make all connections, make sure the suspension is sitting precisely the way it was before disconnecting the battery. Put the wheels back on so you are ready to sit the car back down on its suspension. Connect the battery, lower the car back on its tires. Start the engine so the ASM moves from preliminary mode to stance mode. This will activate the compressor which the ASM will be demanding to reestablish the original ride height. You should get a "ride too low" restriction message as the compressor needs to fill the reservoir plus the entire suspension. Even If the compressor is strong, this can take a while because the ASM times out the compressor to preserve it, keep it from overheating. It will cool back down to a preset temperature before coming back on. Giv it the time while the engine is idling, and...with luck...the fault ride too low will extinguish and you'll be on your way...hopefully not to the dealer.
I've been hesitating answering this because it can become complex and unorthadox without a WDS, or whatever they're calling it these days.
You can pull off the air spring change without reprogrmming the ASM. You have to deviate from the JTIS though. First, you have to understand the basic operating modes and strategies of the AS system. To begin, the ASM will need to be calibrated (suspension height set) only if:
Any height sensor is removed, then reinstalled
The ASM is replaced
or a height sensor is replaced.
While the ASM is active and powered up.
So, you don't want to do any of these, even though JTIS says to remove the height sensor. The ASM is using non-volatile memory to "remember" the inputs of all sensors when it is in certain modes, or when the battery is disconnected. So, you need to outsmart it and create that situation while you are R/Ring the air spring and when the ASM wakes back up.
Briefly, there are five modes the ASM takes depending on "activity". The modes are:
Sleep mode
Preliminary mode
Post mode
Stance mode
Drive mode
You'll be focused on one of these - sleep mode. The ASM goes into sleep mode 30 minutes after the ignition is switched off and the last door or trunk activity is detected. The entire air suspension system shuts down during this time (enters sleep mode) and, if the car is not used, wakes up on a 24 hour clock to check height. At 24 hour intervals, the ASM makes adjustments in height by measuring the lowest sensor and adjusting dwonward so the suspension is even.
Basically, you want to catch the system before sleep mode. You're going to do that by positioning the vehicle where you will work on it, get it raised off the ground and suspended, then disconnect the battery before sleep mode (sooner than 30 minutes after shutting the engine down). By doing this, the ASM will store its inputs from the height sensors with the suspension fully extended. In essence, you're going to perform the surgery on the air springs while the ASM is anesthetized thinking the suspension is in the full extended position. That is what it is going to remember when it wakes up. If it doesn't see that, you'll need to recalibrate the ASM.
Follow most of the JTIS steps now - depressurize the springs, you can use a floor jack to take weight off the airspring, etc., not removing the height sensors. Replace the air springs, make all connections, make sure the suspension is sitting precisely the way it was before disconnecting the battery. Put the wheels back on so you are ready to sit the car back down on its suspension. Connect the battery, lower the car back on its tires. Start the engine so the ASM moves from preliminary mode to stance mode. This will activate the compressor which the ASM will be demanding to reestablish the original ride height. You should get a "ride too low" restriction message as the compressor needs to fill the reservoir plus the entire suspension. Even If the compressor is strong, this can take a while because the ASM times out the compressor to preserve it, keep it from overheating. It will cool back down to a preset temperature before coming back on. Giv it the time while the engine is idling, and...with luck...the fault ride too low will extinguish and you'll be on your way...hopefully not to the dealer.
#2
03-25-2010, 02:52 PM
Almost impossible to evaluate this because it becomes impossible online to judge someone's technical capabilities. Maybe we should create a forum technical expertise scale? 1 to 10, 10 being defined as "factory tech" then each numerical level has a specific definition describing technical capabilities.
If you're mechanically capable, replacing one of these air shocks isn't the end of the world. I'd be more concerned about the dealer diagnostics needed. I know all dealers are different, but in my area, for instance, my dealer isn't too accommodating to DIYers. They have a strong tendancy to "soak" those who want to do some of the work and have the dealer finish up for them.
So, I'd probably begin by clling the dealer first and asking for pricing. Make sure it isn't going to cost as much for diagnostics as just having the delaer do the whole job.
If you're mechanically capable, replacing one of these air shocks isn't the end of the world. I'd be more concerned about the dealer diagnostics needed. I know all dealers are different, but in my area, for instance, my dealer isn't too accommodating to DIYers. They have a strong tendancy to "soak" those who want to do some of the work and have the dealer finish up for them.
So, I'd probably begin by clling the dealer first and asking for pricing. Make sure it isn't going to cost as much for diagnostics as just having the delaer do the whole job.
#3
03-25-2010, 08:48 PM
Stevetech and other interested parties,
Agreed! Damned hard to evaluate tech competance off forum postings. On a scale of 1 to 10 I rate myself a 7 or 8 with the limiting factors being computer applications and and a long of tooth body.
I have rebuilt engines back in the day such as the XJ6, several Chevy 350/455 and a V dub. On my XJR I have done front brakes, replaced a foward control arm on the front and that is about as heavy duty as I want to go given this old back.
Have owned several Jags over the years and always done my own work but I do limit myself to the less demanding chores now days and let the dealers do the really hard and dirty stuff.
Are there any pit falls re to replacing the air springs that you can address, other than dealer cooperation? Buy the way, thanks for that tip as I had not considered it. Such as but not limited to: care and feeding of the new spring, initial airing up of the air spring, likely ride set up of the car on the way to the dealer, special tools, personal safety, etc, etc.
Thanks in advance, My XJ is now sinking in the front 2" every 24 hours. It corrects emediately on start up and is otherwise a pure delite.
Agreed! Damned hard to evaluate tech competance off forum postings. On a scale of 1 to 10 I rate myself a 7 or 8 with the limiting factors being computer applications and and a long of tooth body.
I have rebuilt engines back in the day such as the XJ6, several Chevy 350/455 and a V dub. On my XJR I have done front brakes, replaced a foward control arm on the front and that is about as heavy duty as I want to go given this old back.
Have owned several Jags over the years and always done my own work but I do limit myself to the less demanding chores now days and let the dealers do the really hard and dirty stuff.Are there any pit falls re to replacing the air springs that you can address, other than dealer cooperation? Buy the way, thanks for that tip as I had not considered it. Such as but not limited to: care and feeding of the new spring, initial airing up of the air spring, likely ride set up of the car on the way to the dealer, special tools, personal safety, etc, etc.
Thanks in advance, My XJ is now sinking in the front 2" every 24 hours. It corrects emediately on start up and is otherwise a pure delite.
#5
03-26-2010, 05:52 PM
Stevetech and other interested parties,
Agreed! Damned hard to evaluate tech competance off forum postings. On a scale of 1 to 10 I rate myself a 7 or 8 with the limiting factors being computer applications and and a long of tooth body.
I have rebuilt engines back in the day such as the XJ6, several Chevy 350/455 and a V dub. On my XJR I have done front brakes, replaced a foward control arm on the front and that is about as heavy duty as I want to go given this old back. Have owned several Jags over the years and always done my own work but I do limit myself to the less demanding chores now days and let the dealers do the really hard and dirty stuff.
Are there any pit falls re to replacing the air springs that you can address, other than dealer cooperation? Buy the way, thanks for that tip as I had not considered it.
Such as but not limited to: care and feeding of the new spring, initial airing up of the air spring, likely ride set up of the car on the way to the dealer, special tools, personal safety, etc, etc.
Thanks in advance, My XJ is now sinking in the front 2" every 24 hours. It corrects emediately on start up and is otherwise a pure delite.
Agreed! Damned hard to evaluate tech competance off forum postings. On a scale of 1 to 10 I rate myself a 7 or 8 with the limiting factors being computer applications and and a long of tooth body.
I have rebuilt engines back in the day such as the XJ6, several Chevy 350/455 and a V dub. On my XJR I have done front brakes, replaced a foward control arm on the front and that is about as heavy duty as I want to go given this old back.
Have owned several Jags over the years and always done my own work but I do limit myself to the less demanding chores now days and let the dealers do the really hard and dirty stuff.Are there any pit falls re to replacing the air springs that you can address, other than dealer cooperation? Buy the way, thanks for that tip as I had not considered it.
Such as but not limited to: care and feeding of the new spring, initial airing up of the air spring, likely ride set up of the car on the way to the dealer, special tools, personal safety, etc, etc.
Thanks in advance, My XJ is now sinking in the front 2" every 24 hours. It corrects emediately on start up and is otherwise a pure delite.
Last edited by user 2029223; 03-26-2010 at 06:04 PM.
#6
03-27-2010, 06:28 PM
That's interesting. My 04 XJ8 settles down quickly after shutting down the engine. It immediately rises after starting the engine and runs fine with no error codes. I thought this is what it was supposed to do, to keep high pressure off the system when it is not in use.
#7
03-27-2010, 08:23 PM
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#8
03-27-2010, 09:25 PM
Hi I just noticed that my '04 XJ8 does the same thing,tonight when I shut off the car. I have noticed that at times I can see it raise up when I start it up. Tonight when it lowered I could hear it bleeding air from the system. I'm going to call the dealer Monday and find out if this is normal. My Select warranty expires Monday. They replaced the air compressor last Dec. George.
#9
03-28-2010, 06:57 PM
I think you may have a slow leak. It shouldn't settle down if the engine is running. Check the connections at the shocks.
Last edited by hlgeorge; 03-28-2010 at 07:00 PM.
#10
03-28-2010, 06:59 PM
Hi I just noticed that my '04 XJ8 does the same thing,tonight when I shut off the car. I have noticed that at times I can see it raise up when I start it up. Tonight when it lowered I could hear it bleeding air from the system. I'm going to call the dealer Monday and find out if this is normal. My Select warranty expires Monday. They replaced the air compressor last Dec. George.
#11
03-29-2010, 12:55 PM
Anybody? I really hate to start this chore blind.
Are there any pit falls re to replacing the air springs that you can address, other than dealer cooperation? Buy the way, thanks for that tip as I had not considered it. Such as but not limited to: care and feeding of the new spring, initial airing up of the air spring, likely ride set up of the car on the way to the dealer, special tools, personal safety, etc, etc.
Are there any pit falls re to replacing the air springs that you can address, other than dealer cooperation? Buy the way, thanks for that tip as I had not considered it. Such as but not limited to: care and feeding of the new spring, initial airing up of the air spring, likely ride set up of the car on the way to the dealer, special tools, personal safety, etc, etc.
#12
03-31-2010, 08:50 AM
I think mine is operating normally, I never see it settle down at any time and I do hear it exhale some air now and then when I get out of it after driving. A few times in the years I have owned it, it has risen in the front at a stoplight for some reason. Knowing how the air spring works, I don't think you need to do anything to the system to replace the airspring, it's a dumb component, the ride height sensor is not adjusted in the process, so all that happens is the system fills the spring until the sensor says its at the correct height and that's it. Just pull the old one out and slap the new one in.
#13
03-31-2010, 05:58 PM
Tarheal,
I've been hesitating answering this because it can become complex and unorthadox without a WDS, or whatever they're calling it these days.
You can pull off the air spring change without reprogrmming the ASM. You have to deviate from the JTIS though. First, you have to understand the basic operating modes and strategies of the AS system. To begin, the ASM will need to be calibrated (suspension height set) only if:
Any height sensor is removed, then reinstalled
The ASM is replaced
or a height sensor is replaced.
While the ASM is active and powered up.
So, you don't want to do any of these, even though JTIS says to remove the height sensor. The ASM is using non-volatile memory to "remember" the inputs of all sensors when it is in certain modes, or when the battery is disconnected. So, you need to outsmart it and create that situation while you are R/Ring the air spring and when the ASM wakes back up.
Briefly, there are five modes the ASM takes depending on "activity". The modes are:
Sleep mode
Preliminary mode
Post mode
Stance mode
Drive mode
You'll be focused on one of these - sleep mode. The ASM goes into sleep mode 30 minutes after the ignition is switched off and the last door or trunk activity is detected. The entire air suspension system shuts down during this time (enters sleep mode) and, if the car is not used, wakes up on a 24 hour clock to check height. At 24 hour intervals, the ASM makes adjustments in height by measuring the lowest sensor and adjusting dwonward so the suspension is even.
Basically, you want to catch the system before sleep mode. You're going to do that by positioning the vehicle where you will work on it, get it raised off the ground and suspended, then disconnect the battery before sleep mode (sooner than 30 minutes after shutting the engine down). By doing this, the ASM will store its inputs from the height sensors with the suspension fully extended. In essence, you're going to perform the surgery on the air springs while the ASM is anesthetized thinking the suspension is in the full extended position. That is what it is going to remember when it wakes up. If it doesn't see that, you'll need to recalibrate the ASM.
Follow most of the JTIS steps now - depressurize the springs, you can use a floor jack to take weight off the airspring, etc., not removing the height sensors. Replace the air springs, make all connections, make sure the suspension is sitting precisely the way it was before disconnecting the battery. Put the wheels back on so you are ready to sit the car back down on its suspension. Connect the battery, lower the car back on its tires. Start the engine so the ASM moves from preliminary mode to stance mode. This will activate the compressor which the ASM will be demanding to reestablish the original ride height. You should get a "ride too low" restriction message as the compressor needs to fill the reservoir plus the entire suspension. Even If the compressor is strong, this can take a while because the ASM times out the compressor to preserve it, keep it from overheating. It will cool back down to a preset temperature before coming back on. Giv it the time while the engine is idling, and...with luck...the fault ride too low will extinguish and you'll be on your way...hopefully not to the dealer.
I've been hesitating answering this because it can become complex and unorthadox without a WDS, or whatever they're calling it these days.
You can pull off the air spring change without reprogrmming the ASM. You have to deviate from the JTIS though. First, you have to understand the basic operating modes and strategies of the AS system. To begin, the ASM will need to be calibrated (suspension height set) only if:
Any height sensor is removed, then reinstalled
The ASM is replaced
or a height sensor is replaced.
While the ASM is active and powered up.
So, you don't want to do any of these, even though JTIS says to remove the height sensor. The ASM is using non-volatile memory to "remember" the inputs of all sensors when it is in certain modes, or when the battery is disconnected. So, you need to outsmart it and create that situation while you are R/Ring the air spring and when the ASM wakes back up.
Briefly, there are five modes the ASM takes depending on "activity". The modes are:
Sleep mode
Preliminary mode
Post mode
Stance mode
Drive mode
You'll be focused on one of these - sleep mode. The ASM goes into sleep mode 30 minutes after the ignition is switched off and the last door or trunk activity is detected. The entire air suspension system shuts down during this time (enters sleep mode) and, if the car is not used, wakes up on a 24 hour clock to check height. At 24 hour intervals, the ASM makes adjustments in height by measuring the lowest sensor and adjusting dwonward so the suspension is even.
Basically, you want to catch the system before sleep mode. You're going to do that by positioning the vehicle where you will work on it, get it raised off the ground and suspended, then disconnect the battery before sleep mode (sooner than 30 minutes after shutting the engine down). By doing this, the ASM will store its inputs from the height sensors with the suspension fully extended. In essence, you're going to perform the surgery on the air springs while the ASM is anesthetized thinking the suspension is in the full extended position. That is what it is going to remember when it wakes up. If it doesn't see that, you'll need to recalibrate the ASM.
Follow most of the JTIS steps now - depressurize the springs, you can use a floor jack to take weight off the airspring, etc., not removing the height sensors. Replace the air springs, make all connections, make sure the suspension is sitting precisely the way it was before disconnecting the battery. Put the wheels back on so you are ready to sit the car back down on its suspension. Connect the battery, lower the car back on its tires. Start the engine so the ASM moves from preliminary mode to stance mode. This will activate the compressor which the ASM will be demanding to reestablish the original ride height. You should get a "ride too low" restriction message as the compressor needs to fill the reservoir plus the entire suspension. Even If the compressor is strong, this can take a while because the ASM times out the compressor to preserve it, keep it from overheating. It will cool back down to a preset temperature before coming back on. Giv it the time while the engine is idling, and...with luck...the fault ride too low will extinguish and you'll be on your way...hopefully not to the dealer.
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#15
03-31-2010, 07:17 PM
#17
04-01-2010, 07:05 AM
Veteran Member
#18
04-01-2010, 07:06 AM
I reread my post and forgot something. This is what I meant by complex.
Please add - At the point where you will remove the air spring, you probably will use a floor jack to get the spring off full extension. IT IS IMPORTANT not to hyperextend the the lower control arm with the height sensor in place and the air spring unbolted or removed. DO NOT allow the floor jack to drop below the point at which the air spring was fully extended.
#19
04-02-2010, 08:55 AM
Now we know why the JTIS procedure requires that the height sensor be disconnected prior to removing the air spring.i.e. they figure the car will be on a lift at sholder height and support of the suspension would be a bothersome extra step given that the dealer tech will perform the recal program anyway.
So quick stupid, so late smart.
So quick stupid, so late smart.
#20
04-02-2010, 10:22 AM
Yes Tarheal, you have it figured out.
I've only replaced an air spring twice, both fronts, and I don't have the luxury to play out my theory. I believe that hyperextending the lower control arm with the air spring missing and height sensor in place would destroy the hieght sensor. This sensor is nothing more than a rheostat. When calibrating, the proper physical height is first set then the SDD (or WDS) stores that voltage value from the height sensor in the ASM. When the ASM seeks to restore the proper suspension height in the various modes in which it operates, it adds or subtracts air from the air spring until it sees the proper voltage from that sensor. I believe the WDS has the capability of manually overriding the height sensors and can command the ASM to fill or release air by the corner. Once the proper physical hieght is reached the WDS then saves all the vlotage values of the height sensors (either 3 or 4 depending on MY).
Someone (might have been this site) wanted to lower their car. He said he was successful working with the Jaguar tech setting the physical height at a different dimension, then storing those sensor readings. His car now always adjusts height to that newly specified setting.
I've only replaced an air spring twice, both fronts, and I don't have the luxury to play out my theory. I believe that hyperextending the lower control arm with the air spring missing and height sensor in place would destroy the hieght sensor. This sensor is nothing more than a rheostat. When calibrating, the proper physical height is first set then the SDD (or WDS) stores that voltage value from the height sensor in the ASM. When the ASM seeks to restore the proper suspension height in the various modes in which it operates, it adds or subtracts air from the air spring until it sees the proper voltage from that sensor. I believe the WDS has the capability of manually overriding the height sensors and can command the ASM to fill or release air by the corner. Once the proper physical hieght is reached the WDS then saves all the vlotage values of the height sensors (either 3 or 4 depending on MY).
Someone (might have been this site) wanted to lower their car. He said he was successful working with the Jaguar tech setting the physical height at a different dimension, then storing those sensor readings. His car now always adjusts height to that newly specified setting.