Front air-spring clue emerges..

[Elessee]

This is an '88 LSC... probably 322K miles (maybe 422K). New long block about 40K miles ago. 5L HO engine.. car runs fine in all respects.

On occasion, the front airsprings will deflate overnight. It's been a rare thing. Over the years, I have attempted to trace the system's problem a couple times.. Ran the diagnostics as instructed in the service manuals.. never found anything.. the system checks out 100%. Anyway, I'm pretty much familiar with the spring-system.

But recently a new clue has come to light.

If the car has been parked beyond an hour or so (beyond where controller/airsprings are auto-adjusting themselves although ignition key = off) and IF i put a bag of groceries or similar.. maybe 8 lbs in weight on the left of the hood, overnight the spring will completely deflate.. without fail.
Weight on the left-front hood results in left front spring deflating (right-front seems to hold air. Right side ends up a inch or two higher).

Spring will not deflate if the body is just violently shaken up and down.. there's gotta be some constant, extra weight bearing down on the front end.

I'm thinking the trouble is something with the control module or front leveling sensor, but it's just a wild guess. My thought is the leveling sensors detect a trim imbalance, the control module opens a valve-solenoid and allows a slow leak. However, how could a solenoid open if the entire system is inactive?

Hopefully someone in here is so familiar with this system they might have some idea..

Simply put, extra weight on hood = spring slowly deflates.

This forum helped me a few times. The How-To rebuild the power window motor gearbox was sweet. So, i got faith.

Thanks in advance..

 

[JoshMcMadMac]

It's either a leaking o-ring or the spring itself has a small leak. Start by repeating your test, but turn the air suspension off before doing it. See if the same thing happens.

 

[Elessee]

It's either a leaking o-ring or the spring itself has a small leak. Start by repeating your test, but turn the air suspension off before doing it. See if the same thing happens.

ok.. thanks for the ideas, JoshMcMadMac.

So far, with the suspension switch (in trunk) off, and a weight on the hood, the spring holds air (used a yardstick to measure any body-drop). Then, I turned the switch ON.. Still held air after about 4 hours..
I imagine the whole system reset itself.. Switch = OFF mighta cured whatever was wrong, but i doubt it.

Tonight I fired it up and shut it off.. will let it sit for a hour or two.. then add some weight and see if the problem returns with switch = ON.

I can think of a couple more tests to run over the next day or so.. try and isolate the conditions under which the spring will and won't deflate. Be back with results.

 

[Elessee]

ok.. something changed. I can no longer get the spring to deflate.. Seems that with the system ON-OFF-ON again, it reset itself and is-maybe back to normal. When in doubt, reboot.

Only thing i can figure is a controller error was leaking some current to a solenoid. It cracks open and allows a leak somewhere in the lines. This car's got lots of miles.. the air system lines are old.. a small leak or two is very likely, but makes no difference when the car's running and suspension air pump is active. Otherwise, the bags/solenoids are holding air.

As for recent history:
I had new tires put on about a month ago.. told the guy to be sure and turn off the suspension. He says "yeah" but didn't do it before raising the car (spare tire cover was still in place.. he didnt look there for the "missing" lug nut key, so couldn't have switched it off).
Also put a new battery in about 3 months ago.
Keyless-entry had intermittant problems for about a year and is now non-operational..
a couple other electrical-related minor things.. trunk pull-down motor switch died.. the dash lights now dim when the headlights are on.
One or more of these things may be electrically related to the recent suspension troubles.

man.. I hate it when problems "fix" themselves..

 

[JoshMcMadMac]

man.. I hate it when problems "fix" themselves..

Me too. Just keep an eye on it, and let us know when/if it starts doing it again.

 

[Elessee]

yeah..
in hindsight, i shoulda stuck a voltmeter on that solenoid when the bag was leaking... oh well.. gotta wait till next time.

 

[OldSchool1]

Front air-spring: PROBLEM SOLVED

...
Simply put, extra weight on hood = spring slowly deflates.
...

First, thanks for the complements on the Window Motor Repair article.

Second, Josh reads and responds more than me, but I concur with testing the system in both modes. You can also test the "it only happens when" theory by placing a brick under one front tire overnight and then move the brick under the other front tire overnight and see if there are any changes. If you see the entire front of the car down, then the air spring ~without~ the brick under it has a leak.

Third, bring in the groceries and stop leaving them on the !@#$ hood!