Is there a way of testing the air suspension compressor in order to tell if it is running weak? My suspension is pumping up but I have a feeling the compressor is working to hard to get to trim height.

99 Navigator
4 corner LLS
5.4L SOHC

 

In the past, I removed the airline union fitting just over the abs module in the engine compartment/drivers side (near brake master cylinder) and hooked up a fitting and gage on it. It's easier if you replace the union with one of those Sypder "T" type fittings that Eddie Spinks sells at Americanairsuspension.com. The Spyder has a typical air fill fitting like you would find on a regular car or bike tire - I connected a permanent line on that and ran to a gage I installed in the dash. To do the test, though, you have to rig up a jumper to the compressor to manually run it for no more than 30 seconds, then leave it set for 5 minutes, and take the reading. If the compressor does not reach 110 psi or so and hold it, then it is possible the internals of the compressor are worn. If the compressor does reach 110 psi and holds it, then more than likely you have leaks in the system. There are plenty of places for leaks to develop, you just have to wipe the fittings, lines, connections, solenoids, etc. with soapy water and look for bubbles. Also, the rubber bladder inside the front air shocks as well as the entire rubber air springs are considered a replaceable wear material , they can develop micro-cracks in the rubber that add up to enough leakage to cause the pump to run a lot to keep up with the demand of maintaining ride height. I replaced all 4 at 110k miles, and also replaced the o-rings on two of the fill solenoids and both rear air spring solenoids (each of those rear air spring solenoids has three total o-rings). Air compressor rarely runs now because the leaks are gone, and I can monitor air compressor activity and system pressure from the driver seat. Give those things a try.

 

That is very good information. Everyone with air suspension needs this info. Could you post some pix showing the way you did it?

 

has the pump gotten louder over time? and is that a sign of near death?

 

The compressor has got louder over the last year. I am just looking for a sure fire way of testing it without assuming that a loud compressor means it isn't working efficiently.

 

How difficult are these units to replace. I have a 99 expy 2wd and the compression has gotten obnoxiously loud over the past year and it always seems like it's running. I remember reading somewhere about installing new rubber washers to quiet the unit. Does anyone have detailed instructions on how to replace the compressor?

Thanks.

 

First remove the windshield washer fluid reservoir. Turn off the air suspension switch and remove the 50 amp fuze as a precaution. Then disconnect the electrical connector to the compressor. Disconnect the airline(s) from the air dryer on the compressor. Unbolt the three bolts holding the compressor mounting plate and remove the compressor/mounting plate combo. Remove the old compressor from the mounting plate (3 or 4 screws), replace it with the new compressor and reinstall it. The new compressor will come with new rubber isolation mounts. You can also just replace the rubber mounts if it's just noise you want to alleviate. Turn everything back on and test it out. If it seems like it is always running, either the compressor is worn or you have a leak somewhere in the system, test for leaks with soapy water at joints and solenoids, then replace the tiny o-rings in the solenoids if needed. You may find the rear air springs leaking as well, they are a wear material (rubber) and should be replaced sometime in the early 1/2 of your second 100k miles (I did mine at 112k). Hope that helps. Replacing the components and lines is pretty straightforward.

 

Thanks for the info. Sounds pretty easy. Where is the air suspension switch located?

 

For earlier models it was down in the passenger's kick panel. In later models it was moved to a panel in the left rear of the cargo area.

 

When the compressor seems to run often/long it is usually a sure sign that you have at least 1 leak in the system. The compressor should not be run for more than 3 minutes at a time when the system is being serviced, according to the service manual.
From my experience LOUD should be interpeted as about to fail but, I would replace the mounting insulators first as they are less expensive than a compressor and it's a good experience should you have to go back and replace the compressor later.
The compressors are built with an aluminum con rod and when they finally fail it's because often the rod locks up on the crank shaft and breaks.

 

Thanks for all the great information. I should have been more clear. The compressor does not run all the time when the car is driving. It comes on to pump up the rear and then shuts off when the car is at ride height. It comes back on regularly right after the car is parked in the garage or sitting in the driveway. I don't know if it's supposed to be doing this or not. It also gets extremely hot when it's running.

At this point, I am going back and forth between putting in a new compressor or changing out to standard rear suspension. The install of the new compressor seems easy enough, but potential air leaks may be more difficult to troubleshoot.

Thoughts?

 

At this point, I am going back and forth between putting in a new compressor or changing out to standard rear suspension. The install of the new compressor seems easy enough, but potential air leaks may be more difficult to troubleshoot.

Thoughts?

Stick with the air suspension as it provides the better ride, I have converted Mark VIIIs to springs and am accustomed to them but, the air ride was better. If you are handy and stay with FTE you should be able to overcome the problems that arise from time to time.
Many times a really special vehicle, like a Navigator, is sold or traded in because of a fairly common problem that the dealers only want to charge an arm and a leg to throw parts at. They are not interested in making inexpensive repairs and keeping their customers, they are only interested in the bottom line and will continue to treat us all as suckers that have to pay for ever more expensive parts and often shoddy labor.

 

Checking air leaks take about 20 minutes max to go over the entire system, just requires crawling on your back under the vehicle, not too bad though; obviously, its easier if you can crawl under it in a garage or something and you don't have too much shrapnel in your body acting up (darn that Al Qeda! ).

The routine I use is to make up a spray bottle (empty windex bottle) with about 2 cups of water and maybe 2 tblsp of liquid soap, shake up a bit, then spray it liberally on components in this order (keep in mind, my truck is a 4x4 with 4 corner LLS - if you have a rear-only LLS, just start down the one line from the compressor and work back):
- First, start vehicle and cycle it through R/N/D (with brake on) to get the compressor to pump and level the system, then put it in park and shut off engine.
- With vehicle turned off and in park and the LLS service switch turned off, start at the compressor; spray the line(s) where they enter the air dryer for leak (bubbles with form)
- Move down under the radiator and spray the front fill solenoid (input and output connections)
- Next spray the y-fitting that splits off to the front gate solenoid, and then do that solenoid
- Next spray down the two front air shocks at each line entry point
- Next spray the airline union in the engine compartment for leaks, just above the ABS pump
- Next, on the driver side, mid way down the outside frame rail, spray the rear fill solenoid
- Next, spray both rear air springs and solenoids, the springs are what fail over time due to micro cracks
- Finally, spray the y-fitting that splits the line to each air spring, and spray the vent valve

Each of these connections has an interlocking collet and o-ring that can leak over time with flexing of the body/frame, etc. and just plain age/wear. Replace the o-rings with ones you can order from places like americanairsuspension.com

Last time I did the check (two months ago), I ended up replacing (overhauling) all o-rings (3 total) on each of the two rear air spring fill solenoids. And I replaced the rear fill solenoid o-rings as well. All the others were tight.

I just referrred to Eddie Spinks website for info on how to replace o-rings and do a nominal amount of diagnostics to keep the system going. Try reviewing this source for more help:
American Air Suspension - F.A.Q.'s and Common Expedition or Navigator Air Suspension Problems

Aside from air leaks, there is always degradation that can occur in the control wiring, I'm still running down DTC suspension error codes that come up from wiring circuit to the solenoids going bad from corrosion, it's a pain, but I'm closing the gaps on those problems.

 

Had to bump this thread for my first post!!

I have an 05 Navigator that I had my at the dealer and I had them check the air suspension because the compressor is obnoxiously loud. I figured that there was leak somewhere causing the compressor to run more often and for longer time and it was wearing down or going out and thats why is was so loud. The dealer checked the front suspension for codes and it passed. They then checked it for leaks and according to the paperwork it says "air compressor dryer leak."

I saw that I can buy and compressor dryer online, which I think may fix my leak but I think I have already worn down my compressor. American Air also sells a compressor with a dryer for more but I think this may solve both problems?? Any thoughts?

 

Oh...I sprayed where the dryer connects to the compressor with soapy water and it started bubbling. So I'm going to replace the o-ring but I have a feeling I need to replace the whole compressor.