Weird air suspension problem, any ideas?

Kuda

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My usually trouble-free '97 LSC finally crossed the 100K mile marker this year (purchased in 2004 from the then-president of the National Lincoln Owner's Club). The all original suspension started sagging in the back over night, and the air ride suspension light occasionally came on. No big deal thought I, it's been a good 100K so it needs some love. Got all 4 new bags, new dryer, new compressor, new solenoids, and for good measure, new rear shocks, and had the local garage install everything. Seemed to go well for about 2-3 days, then had *exactly* the same issue: dropped in rear, light comes on intermittently and, when it does, the compressor doesn't kick on. Completely random too, no forecasting when it will work and when it won't. After chasing their tails for a couple of weeks, I picked it up from the local garage and took it to a local Lincoln dealership. The told me their computers wouldn't communicate with the suspension module (obsolete of course), so I tracked down and purchased a known good used module (TBSCShop) and shipped it to the dealership. Once installed...same exact issue. AND now they're telling me it wasn't the module, they just don't have the equipment to communicate with a car this old. After tossing over $2800 into the suspension to get it working, I'm at a loss now. I'm not interested in converting to springs, I'd really like to restore it back to it's former glory. Any ideas, or places in the Baltimore MD/Tri-state area that have the expertise to diagnose and really fix this issue? Any help is very much appreciated!
 
If it were me, I would suspect the air suspension relay. It sounds like the suspension could be triggering to energize the compressor but the solid state relay fails to do its job.

A quick validation test would be to catch the suspension system when it does properly inflate the suspension to normal height and shut off the air suspension switch in the trunk. This will prevent the system from activating to vent or fill the airbags and effectively determine if there is a leak that needs to be tended to. If the suspension stays up overnight (or during a short drive) withe the switch off, you can be reasonably assured there are no leaks causing any issues.

The relay is mounted to the inner passenger fender well behind the wheel liner near the suspension compressor. Last I looked, they were still readily available as they were used on many Lincolns besides the Mark VIII's.
 
If it were me, I would suspect the air suspension relay. It sounds like the suspension could be triggering to energize the compressor but the solid state relay fails to do its job.

A quick validation test would be to catch the suspension system when it does properly inflate the suspension to normal height and shut off the air suspension switch in the trunk. This will prevent the system from activating to vent or fill the airbags and effectively determine if there is a leak that needs to be tended to. If the suspension stays up overnight (or during a short drive) withe the switch off, you can be reasonably assured there are no leaks causing any issues.

The relay is mounted to the inner passenger fender well behind the wheel liner near the suspension compressor. Last I looked, they were still readily available as they were used on many Lincolns besides the Mark VIII's.
Excellent tip! I'm going to give that a shot (turning off the switch). I'll also replace the relay, just in case. Thanks again!
 
My usually trouble-free '97 LSC finally crossed the 100K mile marker this year (purchased in 2004 from the then-president of the National Lincoln Owner's Club). The all original suspension started sagging in the back over night, and the air ride suspension light occasionally came on. No big deal thought I, it's been a good 100K so it needs some love. Got all 4 new bags, new dryer, new compressor, new solenoids, and for good measure, new rear shocks, and had the local garage install everything. Seemed to go well for about 2-3 days, then had *exactly* the same issue: dropped in rear, light comes on intermittently and, when it does, the compressor doesn't kick on. Completely random too, no forecasting when it will work and when it won't. After chasing their tails for a couple of weeks, I picked it up from the local garage and took it to a local Lincoln dealership. The told me their computers wouldn't communicate with the suspension module (obsolete of course), so I tracked down and purchased a known good used module (TBSCShop) and shipped it to the dealership. Once installed...same exact issue. AND now they're telling me it wasn't the module, they just don't have the equipment to communicate with a car this old. After tossing over $2800 into the suspension to get it working, I'm at a loss now. I'm not interested in converting to springs, I'd really like to restore it back to it's former glory. Any ideas, or places in the Baltimore MD/Tri-state area that have the expertise to diagnose and really fix this issue? Any help is very much appreciated!
Hey Cuda, I just went through the very same dilemma as you this past week! However I brought my (97 LSC) chariot to my mechanic and told him my rear end dropped and became an instant Low-Rider, anyway he did the soap and bubbles test and found that the air bags were dry rotted, cracked and leaking. The right one was the worst out of the two, (But not too bad for a 24 year run). So I did some research and found a company by the name of X2 industries that has a wide selection of after market and OEM air ride systems going all the way back to "61" Continentals. I purchased a pair of air bags at the price of $273.00 flat no tax & free shipping! So after a week of diagnoses and trial and error my mechanic went through the schematics and found that the culprit was the rear sensor, so he thought! but it turned out to be faulty pins (5 pins) in the connector. So $500.00 + air bags later....

So the the moral to the story; check the little items that often go overlooked.

Peace from the the East! and have a good one!

P.S. I'm on L.I. N.Y.
 
Hey Kuda, I just went through the very same dilemma as you this past week! However I brought my (97 LSC) chariot to my mechanic and told him my rear end dropped and became an instant Low-Rider, anyway he did the soap and bubbles test and found that the air bags were dry rotted, cracked and leaking. The right one was the worst out of the two, (But not too bad for a 24 year run). So I did some research and found a company by the name of X2 industries that has a wide selection of after market and OEM air ride systems going all the way back to "61" Continentals. I purchased a pair of air bags at the price of $273.00 flat no tax & free shipping! So after a week of diagnoses and trial and error my mechanic went through the schematics and found that the culprit was the rear sensor, so he thought! but it turned out to be faulty pins (5 pins) in the connector. So $500.00 + air bags later....

So the the moral to the story; check the little items that often go overlooked.

Peace from the the East! and have a good one!

P.S. I'm on L.I. N.Y.
 
Here's a link to electrically testing the compressor, solenoids, and vent valve if you're good with electrickery. If that all checks out and you replaced the airsprings and compressor, you might have a leak at one of the fittings. You could test for leaks by opening the solenoids one at a time, and running the compressor and have someone else check at the compressor and solenoids for leaks. I recently ran into this when changing out a compressor, one of the airlines wasn't fully pushed into the push to connect fittings, you can feel it leaking when the compressor is running.
Here's the link:
 
"A quick validation test would be to catch the suspension system when it does properly inflate the suspension to normal height and shut off the air suspension switch in the trunk. This will prevent the system from activating to vent or fill the airbags and effectively determine if there is a leak that needs to be tended to. If the suspension stays up overnight (or during a short drive) withe the switch off, you can be reasonably assured there are no leaks causing any issues."

I realize that this is an old post, and I am a newbie here, but I have been scouring all Mark VIII air ride information and saw this.

I have a 1998 LSC, 104,200 miles and it has been a good car during my ownership (2011). I jacked up the car to check the brakes prior to leaving for Idaho. Used a floor jack, back then front, with the main AR switch off. When I lowered the car, prior to turning the switch on. the rear sat at normal height, but the front was probably a good 8/10" high. I let it sit, turned the switch back on, started the car and drove it over to the barrage and parked it for the night. Sometime later the car was down to normal height; 3 days later it was down completely in the front. So, I allowed the bags to fill upon start, shut the switch off, drove the car for 30/40 miles, parked and the car never lowered across 6 days. Once the switch is turned on, the car will drop in the front just about 48 hours.

I cannot find any leak, and the 'validation test' seems to further prove that out. It seems as though the system didn't initially vent, thus the high nose, and now it fails in the other extreme. The only possibilities I can think of are;

1. Solenoids possibly need replacement.
2. Height sensor issue.
3. Air ride module acting up...

Without a Rotunda SS II, and being somewhat limited on electrical issues, at this point it looks like hard part replacement as supply will allow; when parking the car for days at a time shutting the AR switch off; or putting the car up for sale and letting someone else enjoin the challenge.

The shop I leaned on for the troubles such as this have seen all the experienced mechanics leave and the younger guys are lost. Any further input is appreciated.
 
The first symptoms make no sense. If the air ride is switched off and the car jacked up, there should be no change when the car is returned to the ground.

None the less, from your description it sounds like an intermittent problem, which makes troubleshooting extremely problematic. So, without the Rotunda SS II diagnostics, we're grasping at straws. :(

I would tend to suspect an intermittent venting malfunction. One possible source would be the vent valve which is integral to the compressor. The typical issue with the vent valve is sticking... either partially or fully. If you think through the normal air ride processes and throw in vent valve not functioning as it should because of a sticky valve... you can begin to comprehend the various displayed symptoms.
 
Thanks...I agree with your take, especially with the 'first symptoms' and the only possibility that crossed my mind is the switch wasn't actually off though positionally pressed to be; once pressed back on there was no reponse from the compressor...until after I came in the house.

I figure it out, I'll let you know.
 
When you jack up the car then lower it back down, the car will be higher than normal because the wheels are at a slight angle from being jacked up. Just drive the car down then up the driveway and it will go back to normal. If the car doesn't leak down after you shut the switch off when at driving height, and does leak down if you let it go to parked height then turn the switch off, then airsprings have leaks. They usually leak first at parked height as that's where the folds in the airsprings are most of the time. When I have airsprings that leak I always leave the switch off (at driving height) to keep them from leaking too much until I can replace them. I still need to pump them up every once in a while though, as that only gets a little more out of them. The solenoids don't usually start leaking unless they have been recently removed.
 
Thanks Bill. I need to get it up in the air and check the 'fold' area more carefully. So far, no indications of bag leak other than the results.

I do understand your point about toe in/out upon setting the car back on the concrete, however, this was well beyond that at 8/10" in height.

Again, thank you for your thoughtful response.
 
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