What should you leak test?
To be successful in diagnosing your air suspension problem, you have to first figure out what to test. While everyone wants to think that the reason their 50K SUV is going down is because of something cheap & simple like a leak at the dryer or solenoid, in reality, this just isn't the REAL problem!
If you look in a Ford shop manual, it says in black & white that the line connections were never designed to be totally leak-free. The reason they don't care if they have a small leak at a line connection, is because of the solenoids. These vehicles have a solenoid on each air spring that acts as a gate for air and are normally closed. These solenoids are a very good, dependable design and very rarely fail. Air is held in the Lincoln Air Bags by a solenoid and it is designed to remain in the airbag until the module signals a solenoid to open. At this time, the air will either go in the airbag or back out.....depending on what the module is trying to accomplish. The module(brain) makes ALL the decisions based on the info that the height sensors have given it.
While these systems are designed from the factory to be able to make any adjustments for an hour or two after shut down, they are also designed to go to sleep or shutdown after this time. During this off-time, the system won't make any adjustments and really doesn't give a hoot what the car is doing.
TO FIND OUT WHAT TO FOCUS YOUR EFFORTS ON, USE THIS AS A CHEAT SHEET:
If the vehicle you're working on goes down after the vehicle has sat a while, turn on the ignition to see if it'll pump back up. If the air suspension compressor IS able to pump the car back up, focus your efforts on the Lincoln Air Bags or the 2 solenoid seals the size of your pinky, that seals the solenoid to the airbag.
Forget about any leaks in the airlines, where the line goes in the solenoid or dryer, as a leak in the lines just makes the system less efficient and will only increase raising the time of your vehicle.
In other words, if it can pump up, apparently any leaks in the lines weren't severe enough to cause any problems. Also, if the system usually pumps up the vehicle in say....20 seconds, it may now take 25-30 seconds because of the leak at the line connection!
If the vehicle you're working on goes down after the vehicle has sat awhile, turn on the ignition to see if it'll pump back up. If it DOES NOT pump back up, first find out if the Lincoln air suspension compressor is running.
If the Lincoln air suspension compressor IS running, a pretty severe leak at a line connection and/or weak compressor maybe at fault.
If the Lincoln air suspension compressor is NOT running, focus your efforts on why it's not coming on, as a bad air suspension compressor relay maybe dropping the ball or the module is seeing a problem in the system and is trying to shut down the system.
First of all, the rubber used on Lincoln Air Bags gets dry rotted mostly on the fold of the rubber, or where the rubber folds around on the bottom. This folded area of the rubber gets the blunt of the punishment and dry rots at a much faster rate than the rest of the rubber. Because this area dry rots faster than the rest, this is where your leak is going to be the majority of the time.
The reason the Lincoln Air Bags will leak sometimes and not other times, has a lot to do with temperature and most importantly, where the fold of the rubber is. The area of the rubber that's on the fold, will change with vehicle height. In other words, the fold of the rubber will be in a different area while the car is being driven (city height) as opposed to when it is sitting still (vented or parked height). If the dry rotted area of the rubber is On the Fold, this will expose and open any cracks in the rubber and allow air to escape.
Keep in mind that ALL the Lincoln Air Bags have their own solenoid. The solenoid acts as a gate for air and no air should go in or out unless the solenoid is opened up by the module. By turning the suspension switch off, you're disabling the solenoids, thus no air should escape....unless of course there's a leak.
RECOMMENDED LEAK TEST OF LINCOLN AIR BAGS
By far, the easiest way to test for a leak on a Lincoln Airbag, is to allow the car to vent down after shutting off the engine and opening and closing the door.
IT IS VERY IMPORTANT TO MAKE SURE THE CAR HAS LOWERED PRIOR TO TURNING THE SUSPENSION SWITCH OFF, OR THE TEST WON'T BE ACCURATE! Your goal is to get the vehicle to sit at the height it sat at most of it's life.
If nothing else, wait 5 minutes after you turn the ignition off...then turn the suspension switch off. The car should have vented by then.
After this, turn the suspension switch off and measure the height of the 4 corners of the car with a tape measure and write it down. Now drive the vehicle for a few days. If the vehicle has a leak, the car should go down after driving.
NOTE: Depending on the severity of the leak, it may take more than one day to leak down. This is the case more times than you would think.
By all means, if the car goes down after 10 minutes of driving, turn the switch back and resume your journey. You have answered your question.
COULD IT BE JUST A SOLENOID LEAK?
It's been my experience as a former Ford/Lincoln factory trained and certified technician, that if the solenoid has never been removed before, most likely the leak isn't from the o-rings that seal the solenoid to the Lincoln Airbag. Now if the solenoid had EVER been removed before, the o-rings should have been replaced at that time. If you have an old o-ring that has never seen the light of day and all of the sudden, after 10 years of being cooped up, it is released from tension, it will expand. If reused, it WILL eventually cause a leak . It might take a day, a month, or even a year, but it WILL leak at some time down the road.
In other words, if you replace your Lincoln Air Bags, make sure you replace the 2 x o-rings that seal the solenoid to the airbag. If you don't, it's not a matter of IF it will leak, but more like WHEN. It would be in your best interest to also replace the little o-ring that seals the air line to the solenoid at the same time. Because this o-ring is AFTER the actual sealing part of the solenoid, if this o-ring leaks, it will only affect the operation of the system while the solenoid is opened, like when the module is making a height adjustment. Not while sitting overnight!
RECOMMENDED LEAK TEST OF THE AIRLINES
Leak testing the airlines of a Ford or Lincoln is fairly straightforward. By simply spraying a soapy water solution, comprised of a shot of dishwashing soap & water, this will show you where small air leaks are. You just look for the bubbles.
REMEMBER, leaks in the airlines whether it's the line going in the solenoid or dryer, just makes the system less efficient and will only increase raising the time of your vehicle.
In other words, if the vehicle can pump itself up, apparently any leaks in the lines weren't severe enough to cause any problems. Also, if the system usually pumps up the vehicle in say....20 seconds, it may now take 25-30 seconds because of the leak at a line connection!