Looking for help with my 97 Mark VIII air ride system

mbe

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For just short of a year now we've been fighting this one on and off. The problem is that the front half of the air ride system on my wife's '97 Lincoln Mark VIII may or may not inflate. Currently,it is refusing to inflate and the front end is completely all the way down. About a year ago the front end began to deflate whenever you turned off the car. Sometimes it was quite quickly and other times it was sometime over night. Upon startng the car the front half would reinflate with no further problems until you shut it off. I thought it was just a slow air leak and with the car running, the compressor would keep it pumped up. However,later on and quite by chance I discovered that after turning off the car you can hear a click like that of a light switch somewhere under the hood and then the sound of escaping air and the front system completely deflates. But, again, it would reinflate after starting the car. At a point in time later on it started to refuse to reinflate. At this point, the compressor would run (it's new) and the rear half would rise slightly from its normal hight. When the compressor would finally shut off, the front end would still be down and the rear would settle to the proper ride hight. So, I took it to the dealership and they plugged their machine (a computer of some kind I suppose)into the air ride system and ran it through a series of commands and of course the system preformed flawlessly including reinflating the front end. The end result was that they had no clue as to what was wrong with the system as it preformed all tests perfectly. Over the next several months I went through the same thing 3 more times at the dealership and always the same result...no one has a real clue. They did offer a guess and said that one of the computer boxes is malfunctioning but offered no guess as to which one. Apparently there is one behind the right front kick panel and one under the back dash in the trunk. In July after the last trip to the shop and with the system fully inflated I turned the system switch to off. The system stayed inflated with no air leaks until late December when I noticed the car had settled about 1/4 down at both ends. I guessed that the cold winter weather of South Dakota had shrunk the seals and was letting air slowly escape. So, here goes nothing, I turned on the system and I was in luck as all 4 corners reinflated to the proper hight. At the end of Feburary I noticed it was slowly settling again in the now super cold weather. So I turned the system switch to on and the compressor kicked in and reinflated the rear half, but the front half didn't move and stayed at the same position it was in at about 1/2 to 3/4 inflated. Like a blockhead that I can be, I shut the car off without first turning off the air ride system switch...big mistake! I heard the familiar click sound from somewhere under the hood and all of the air was released from the front end almost putting the front bumper on the ground. Here again the compressor runs until it times out and shuts off without reinflating the front end. I made several more attempts including bouncing the front end in hopes that the hight sensors might kick in, but no such luck! It now just simply refuses to reinflate the front half of the system.
I'm at my wits end and I don't want to spend a ton of money going back to the dealership for another round of "I don't know what's wrong with your air ride system, but here's your bill anyway". If I have to replace one of the computer boxes, I want to replace the right one the first time as they're expensive. Can anyone here at LOD tell me what's wrong and what I need to do to repair it? A friend of mine said about a half stick of dynamite would fix up the problem quite nicely......I'm starting to agree!!
Also, I was told that there is an air valve somewhat like a tire valve stem someplace in the air lines that I can use to pump up the system in case of an emergency. Is this true? If so, where will I locate this air valve? And what is the correct air pressue?
 
A lot of questions, but I'll try to help.

For a general understanding of the system, check out these links...

http://www.lincolnmarkviii.org/suspension/asexplained.htm

www.americanairsuspension.com

It sounds to me like your vent valve on the compressor is sticking. What happens is the valve opens to vent the system down to parked height but sticks. A common malady too often that baffles even the dealers.

I hope this helps you get started in the right direction anyways.
 
Hi Driller, Thanks for your input! I have checked out the sites that you have mentioned before along with several other sites, but I have come up empty handed. If I comprehend correctly what I have been reading up on, It shouldn't really matter if the vent valve is sticking open or not providing of course that the air bag solenoid is closed preventing the contained air in the bag from escaping out the open vent valve.
It is my theory that one or both front height sensors are sending incorrect signals or that the ECU is failing to correctly read the signals from the height sensors. If either is true, proper control of the air bag solenoids would be nonexistant....any ideas?
 
You're not understanding what you are reading if I am reading your symptoms correctly. When the vent valve is stuck, the car cannot pump back up since the compressor is pumping through the open vent valve.

This may help... SELF TEST LINK
 
Hi Driller, Thanks for your reply. At the risk of sounding like or being a pain in the neck as it is not my intention, but I do have to ask a question about your last post to me. If the vent valve is stuck open would this not then affect the function of the rear bags? As I noted in my opening thread the rear bags are still inflated and when the car is started the compressor runs and there is a slight rise of the rear bags. When the compressor shuts down the rear bags settle slightly to the proper ride height. Can this happen if the vent valve is in the open position? Again, I really don't mean to be a pain about your vent valve theory, I really am just trying to get things clear in my mind before tearing into this thing.
 
In all honesty, I think you may have multiple issues but your PRIMARY issue is the car will not rise to ride height. The vent valve being stuck prevents this because when you start the car, the normal operation is to inflate the front bags to raise the front FIRST and with the vent valve stuck open - it cannot raise the front end because it opens the front bag solenoids and they then bleed through the system back to the vent valve, the same as when it normally vents to 'parked' position. Wala! The car is slammed in the front and the compressor times out. Here's the scenario...

  1. Park car and exit vehicle.
  2. Car drops to parked height.
  3. All solenoids close but the vent valve is stuck.
  4. Enter and start car.
  5. Compressor starts.
  6. Vent valve stuck open vents air from front bags because front solenoids open ready to inflate.
  7. Car is hopelessy slammed.
  8. Compressor times out.
You can remove with care, clean and reassemble the offending part. A search here should show that very thing done by member "wvabeer".
 
Hi Driller, Thanks for your continued help and suggestions! You can be sure that I'll be checking the vent valve. It's not too difficult to remove and replace the compressor as I did install the new compressor. Sure would be nice to have a hoist to do it though. I'll let you know how it comes out. Currently I'm waiting on the bearings for the telescoping steering column to arrive. Ford managed to send the wrong bearings the first go 'round so had to do a reorder this past Saturday. Hopefully, by the end of this comming week I'll have the parts to put the column together and have an electrical system again. I'll send a thread in a week or so to let you know my findings.
Again, my thanks for your help and patience with me on this project!
 
I did skim a lot of this thread, so forgive me if i'm being redundant.

If the vent valve sticks open, when the car lowers upon shutting it off, it should stop lowering when the valves on the bags are closed, But if it goes down too far, the system will try to pump it back up for a while after the car is shut off. If the vent valve is stuck open, when it opens the wheel valves to pump it back up, the car will just sink further.

If the vent solenoid just sticks intermittantly, it might not show up on a scan at the dealer. After all, intermittant problems always go away when the mechanic looks at the car, i think that's one of murphy's laws.
 
I think that this could also be leaking front airsprings.

I'd try jacking the front end up just a couple of inches and try it again. Don't jack it up too much, as you don't want the car near the correct height. You want the compressor to run, to bring it up off of the jack. You might have to cycle the key on and off a couple of times to fill the airsprings.

It's an easy thing to try. If you can't get your jack under the car, drive the front tires onto some long wood blocks first.
 
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