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post #1 of 13 (permalink) Old 05-01-2018, 10:39 AM Thread Starter
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Air suspension fun

So I had the air suspension on the old 93 Mark some 5-6 years ago - it suffered from leaky front airbags and solenoids, which after replacing (along with a compressor) made the car quite a pleasure to drive. My 96 was converted to coils before I bought it, and it was nice to have the maintenance free aspect but I did occasionally miss the novelty of the adjusting ride height and the self leveling trait due to varying loads. The ride characteristics also seemed much better with the air suspension which I also came to miss.

Now, this 98.

I bought it and the original owner had the front two air springs/shocks and compressor replaced before I got my hands on it. It doesn't leak (that I can tell), but there are still some gremlins that I'm trying to hunt down. I wanted to present my findings and thoughts here for whoever's left that has any experience with these. This will be a fairly long winded and detailed post, so bear with me.

Background on the system and its operation, for those not familiar and potentially looking to weigh in -

The system has four air bags (one at each corner) each with a solenoid to allow air in or out, three ride height sensors (front corners and one at the driver's rear to measure rear ride height), the compressor, and a control module. The system maintains two different ride heights - city height and parked/freeway height (1/2" lower than city height). It's supposed to pump itself up to city height after you open and close the driver's door, then turn the ignition on. It maintains that height until you get to freeway speed (60-65 MPH), then it vents to parked/freeway height. It will maintain that height until the car slows down (48 MPH or so), after which it will pump back up to city height. It also adjusts to changes in loading to maintain a level stance (e.g. you dump a bunch of weight in the trunk so it pumps up the rear to compensate).

If the suspension control module is trying to raise the car and after 90 seconds doesn't see the change completed, it triggers a "check air ride" warning and disables the system until next key cycle. If it is trying to lower the car and doesn't see the change completed after 45 seconds, it does the same.

Now for my symptoms.

Item one - the car doesn't always pump up to city height after I get in, close the door, and start the engine. I don't get a check air ride message on the message center. It doesn't vent back down to parked height after I get to where I'm going, shut the engine off, and exit the car/close the door. If I take the car up to freeway speeds and maintain it for a few minutes, it will eventually trigger the check air ride warning. I can drive this way for at least a couple hours, and it wasn't low when I parked the car (did this on my way home from Michigan with it).

Item two - most of the time (maybe 60-70%) it will pump itself up after I start the car (as it should) and it acts normally while driving in the city. If I take it up to freeway speeds and allow it to lower, but return to city speeds, it will raise the car again within a couple minutes, and it continues to act normally without triggering any warnings.

Item three - sometimes, if it doesn't pump up after I start up and get in, I've shut the key off and restarted the car while waiting at a traffic light, and it pumps up right away.

Item four - I initially suspected a bad or intermittent relay. I bought and installed a used one off a guy parting out another 98 locally, and there was no change - so I am assuming the relay/connection to the relay is not the problem here. The compressor is new, so I also assume that is not the problem.

Item five - if it behaves normally, it will always trigger the check suspension warning after I've had it at freeway speeds for 5-10 minutes.

My understanding was problems with the components would trigger the suspension warning message 90 or 45 seconds after a commanded event, due to the pump/vent timeouts. My suspension warning messages always come on at weird times, several minutes after any commanded changes in ride height.

I bought two new rear air bags when I bought brake parts, just for the heck of it. Is it possible there's a slow leak at certain ride heights in one of them, which causes the suspension to see the rear of the car go low after a few minutes at freeway heights and throw the error? If so why would it do that instead of just pumping back up; does it not make adjustments to ride height at freeway speeds? Part of me is leaning towards an intermittently faulty suspension control module (which I understand is rare), or connection to it. I jiggled the wires to it a little but there doesn't seem to have been any change in symptoms.

I've been combing through the troubleshooting articles on the archived versions of Eddie Spinks's americanairsuspension.com (https://web.archive.org/web/20101116...III%20AREA.htm) for ideas, but all seem to point to that 45 or 90 second timeout which isn't leading me anywhere that I can tell. Sadly I don't think that air suspension test tool is available for loan anymore either!

Maybe I should just get the new rear air bags in and see what happens...

-Brandon
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post #2 of 13 (permalink) Old 05-01-2018, 11:30 AM
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The thing I see is that all four lines have a venting problem, as you didn't mention corner drop problems.

All 4 lines come together at the dryer, a container of silica gel, most likely.

If that gets wet, from a leak that was repaired, it could be a semi-liquid gel.

I'd disconnect all 4 lines at the drier, and see if it vents freely; if it does, reassemble, and see if it re-inflates ok.

If it then fails to vent properly, it's likely the drier.

If it's filled with silica gel, you could put it in your oven at 200 degrees overnight, and see if it solidifies and clears the blockage.

Replacement is easier.

My read of the web points to either the drier or the vent solenoid in the compressor.

BTW, that Rotunda tool is a Code reader, from my looking on ebay, and they say it's eec-iv, which your 98 is not.

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post #3 of 13 (permalink) Old 05-01-2018, 03:57 PM
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An airbag definitely can leak at one ride height, and not (or rather not much) at another, but if it leaked at freeway/parked height, especially enough to trigger a check air ride message, then your car would be on the ground when you came out to it in the morning. I would sooner suspect that one of the ride height sensors is cutting out at a certain height. A quick test would be to do the sensor lower mod, which involves moving the bracket for the sensor so that the car thinks it is higher than it actually is, which will lower the car slightly. If doing this eliminates, or significantly lessens the problem, then I would test each sensor to see if one of them has a dead spot. Another thing to keep in mind, the air ride module needs to see the input from the door switch, and sometimes those switches go bad. I have never seen one cause a check air ride error, but I have seen it not function, and with no input from the door switch, the system will never change ride heights.
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post #4 of 13 (permalink) Old 05-01-2018, 05:38 PM
No, Mr. Lemmywinks, No!!!

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Quote:
Originally Posted by MadMikeyL View Post
... with no input from the door switch, the system will never change ride heights.
I've seen the door switches freak out on my car with the door indicators, while driving.

Back in the day, when people thought they wanted talking cars, a co-worker drove a plymouth laser from memphis to knoxville with it saying "the door is ajar" every 15 seconds, lol.

The fuse that ran the voice ran the spark, lol.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
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post #5 of 13 (permalink) Old 05-01-2018, 07:30 PM Thread Starter
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Thanks for the input and set of fresh eyes guys. From closer observations today, most of the day it wasn't acting right. It didn't pump up this morning and for all but two startups (one in the middle of the day and one just before coming home). Right before I fired it up that last time, I noticed the right rear corner looked a little low. I think this weekend (or earlier, if I can get off my lazy hind end) I'll tackle the rear air bags since I've got the parts handy. While I've got the thing apart I'll pull the rear sensor off and ohm it out across the range (assuming it should be a nice, even and linear scale) and see what it comes up with.

I also hadn't thought about the door sensors... the 96 and 93 both gave me headaches on that count!! This one hasn't shown me any door ajar lights and the interior lights turn off when closing the door like usual. I had taken that to mean all was well, but thanks for putting the fresh perspective on that and making sure I keep those on my radar as well.

Grog - I didn't think a whole lot about the vent solenoid or the dryer either. Putting it plainly I have heard solenoids click and the car doesn't lower sometimes, and sometimes it does. Maybe the vent solenoid at the compressor? Hmm. Lots to think of and mull over... I've got the EVTM for the 96 so maybe I'll hunt down the wires for the compressor relay and vent solenoids and tap into them to see what the control module is commanding (and when!) to see if that can help me determine what's causing the fault.

-Brandon
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post #6 of 13 (permalink) Old 05-01-2018, 10:12 PM
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Quote:
Originally Posted by Grog6 View Post
I've seen the door switches freak out on my car with the door indicators, while driving.

Back in the day, when people thought they wanted talking cars, a co-worker drove a plymouth laser from memphis to knoxville with it saying "the door is ajar" every 15 seconds, lol.

The fuse that ran the voice ran the spark, lol.
I can only hear Eddie Murphy's voice when reading that!

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post #7 of 13 (permalink) Old 05-18-2018, 03:06 PM Thread Starter
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Well, some progress.

I got my hands on one of the "super star II" testers referenced in the air suspension testing procedures I found online, and went through the tests (pumping and venting each solenoid individually) and what I found was....

LF, RF and rear will pump fine. Ride height sensors work fine - they properly indicate trim height, too high, too low etc. consistently.

RF and rear will vent fine. LF will not vent, and there's a code 99 in memory (failed to detect raising or lowering - in this case, lowering of that corner). The solenoid at the air bag clicks and I know the vent solenoid at the compressor works (venting the other three air bags works properly), but that one side doesn't go down. No pressure in the line between the bag and the compressor vent solenoid either.

Clogged dryer? If so why does it only affect the one corner?

Right now that one corner is about an inch too high because of all the fooling around I've done. I'm going to let the air out by loosening the solenoid, and let it go to trim height so the car doesn't look (or handle) like crap until I can get the rest sorted.

-Brandon
97 Laser Red Thunderbird LX 162k, Stage 2 4.6L 2v N/A | 300 BHP (255 RWHP, 290 RWTQ) | 13.95 @ 97.58 | Build details | Pics at the Lorain Assembly plant
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Gone but not forgotten: 96 Mark VIII, 94 Cougar XR7, 93 Mark VIII

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post #8 of 13 (permalink) Old 05-18-2018, 03:22 PM
No, Mr. Lemmywinks, No!!!

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It looks like the compressor can supply enough pressure to make it pump up, but the stored pressure wont vent.

Try loosening the connections, and running a wire thru the ports where pressure is retained; you could compare how it acts to one of the others.

A rusty fitting will cause this; acting like a flapper valve.

I'm betting it will go 'whoosh' when you hit the right spot.

Red '96 Cougar XR-7 240k mi. '02 4R70W, PST DS : '03 PI engine, 04 maf, 24lb injectors, 2.5" exhaust, '02 4r70w + Jmod, DirtyD0g TC + cooler + 3/8" lines, 255 walbro fp. Alpine system.
Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
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post #9 of 13 (permalink) Old 05-18-2018, 03:55 PM
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Remove the selenoids from the bags and clean them out,clean out the dryer and inspect all 0 rings..i had a LOT of strange issues with mine leveling incorrectly and I finally fixed it by venting the complete system,disconnecting the battery over night then letting it refill and while it fills make sure you are on complete level ground and stand in the trunk and bounce it down as hard as you can while the system is inflating .
Yes,I know I laghed too but the guy swore by it and we tried it on mine and it fixed it..my system initially got out of whack because I towed the car 500miles with the air ride switch on,key on in ignition because I kept it in neutral and would pull over and run the trans pump every hour jutst encase I was warming up fluids towing in neutral ( long debate)
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post #10 of 13 (permalink) Old 05-18-2018, 04:31 PM Thread Starter
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Round 2 of advanced troubleshooting reveals...

If I disconnect the LF solenoid and tell the computer to vent that corner, I hear the vent solenoid click at the compressor. If I plug the electrical connection back into the LF air bag solenoid I can hear and feel it click but no air passes through it. So I removed the solenoid from the air bag and told it to pump air to that corner. Barely any pressure came out of the thing - I was able to put my finger over the top and stop the flow.

Based on the fact that (from what I've read) the compressor is supposed to push upwards of 100 PSI through the solenoids, and the air bags will typically be between 30 and 50 PSI, it makes sense that it would work one way and not the other in the way I found. So clogged vent solenoid it is! Time to get one of those ordered. The best part is, I don't even need to pull the tire to replace it!

-Brandon
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Last edited by theterminator93; 05-18-2018 at 04:41 PM.
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post #11 of 13 (permalink) Old 05-18-2018, 05:38 PM
No, Mr. Lemmywinks, No!!!

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Questions:

Will it come apart?

It's likely a variation on a needle valve, and it's problem is that either it's rusted, or the parts are worn.

I'd disassemble, if possible; if it reduces to metal, then carb cleaner and knocker-loose will de-rust it, and make it work again.

An o-ring may be involved; that would be even easier.

You've taken laptops apart, so you have the skills; IF it's rebuildable.

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Black '96 Cougar XR-7 (Lazarus) 210k mi PI Intake, '02 4R70W, Jmod, PST DS, GrogTune, Konis, Mark LCA+Poly, racecougar Custom Engine Chain, and JL and racecougar Bracing.
Black '97 Tbird Limited Edition, '02 4R70W, 255 walbro, PST DS, PBR Brakes&SS lines, Toicko Blues & Springs, GrogTune.


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post #12 of 13 (permalink) Old 05-18-2018, 06:47 PM Thread Starter
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I didn't see an obvious way to get it apart, but I managed to find one on feeBay for like $11 so I've got a replacement enroute.

Once I get that one on the car and verify that it fixed the problem(s) I'll rip apart the old one if I can find a way inside that doesn't involve a band saw.

-Brandon
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07 Redfire Fusion V6 SEL 178k, for the wife
Gone but not forgotten: 96 Mark VIII, 94 Cougar XR7, 93 Mark VIII

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post #13 of 13 (permalink) Old 05-23-2018, 04:26 PM Thread Starter
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Well, the $11 solenoid I bought off eBay arrived a day early and I popped that on this afternoon and tested it. As hoped, that corner now pumps and vents properly.

I haven't taken the car for a test drive yet but this should fix all the issues.

Now, to get that left UCA replaced (noticed it was very much shot today!)...

-Brandon
97 Laser Red Thunderbird LX 162k, Stage 2 4.6L 2v N/A | 300 BHP (255 RWHP, 290 RWTQ) | 13.95 @ 97.58 | Build details | Pics at the Lorain Assembly plant
98 Black Mark VIII 160k, stock daily driver
07 Redfire Fusion V6 SEL 178k, for the wife
Gone but not forgotten: 96 Mark VIII, 94 Cougar XR7, 93 Mark VIII

TCCoA's resident pilot since 2014
Once you have tasted flight, you will walk the world with your eyes turned skyward, for there you have been and there you long to return. -Leonardo da Vinci
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