Only lowered it once and didn't time it... but that was lowering it all the way down to the stops. My guesstimate on time may be way off... I tried it last night again, in case you were right on the pump overheating and cutting out, but I can not get the pump to start. I'm thinking at this point, maybe the compressor is prevented from starting up under pressure. I found where in the IID tool to look at the system pressure and after deflating everything, it says there is still 60 psi in the tank. the friend that was going to come help had an emergency and couldn't make it, so I'll have to wait on him to be freed up and then we can get into testing , trouble shooting and clearing lines, valves, inlet filter and exhaust. Not much more I can do by myself till I get another set of hands , so it's just going to have to sit for now and will up date soon.

 

There actually is no reservoir tank sensor, the pressure sensor is at the center valve block and measures gallery pressure. The gallery is normally isolated from the reservoir unless air is needed. Typically the gallery leaks down, which is fine. Like you said if there is too much pressure the compressor can not start up. In fact before the compressor starts the system is command to briefly vent gallery pressure, which is why if it has pressure you can hear a brief "fart" before the compressor starts up. And you also often hear it fart after the compressor stops.

Wish I was closer, I would dive right into things and sort it out for you. A lot easier with eyes right on it.

 

You are only less than a 10 hr drive away... When can I expect you ? LOL. Just kidding, but that would be great. This is a real learning experience for me hopefully I will feel a great sense of satisfaction when the mystery is solved and things are working right. If I didn't have the 2 back injuries I have, one being a broken back, I would be making better time on this with hands on. As it is, I have to rely upon a second set of helping hands which takes longer to accomplish things under the beast. The more you share, the more I learn and gather insight. Trust me when I say, I appreciate every bit you share. Stay tuned for the next update.
Thank you again.

 

Well... we spent 3 hours on it and near as we can figure at this point, the air dampening valve assembly for the reservoir now appears to be the culprit with 2 issues. One issue being the pressure sending unit is out of calibration by nearly 35 psi. Secondly, the Solenoid valve is not functioning consistently. Amazon has that valve assy complete for $102. but it may not show up till mid sept... Too long away to wait, so I ordered one from the stealer dealer for $320. Should be in next week and fingers crossed... that will be the end of it.

 

How did you figure the pressure sensor was off?

Odd the valve could be bad, but I suppose if the system inflates and fills the reservoir, but the valve is leaking it would sorta feedback into the system when venting, causing things to more or less stay air up longer than they should. Hmmm...

 

In the process of trouble shooting, my IID tool was still reading nearly 40 psi on a completely empty gallery. We pulled the connection and the IID dropped to 2.8 lbs which I thought should have been 0 psi, but 2.8 psi I would think would be acceptable. The solenoid was inconsistent , sometimes snapping open and closed cleanly, other times, just humming and buzzing.
Also with the pressure sending unit being way off, sending the wrong information to the computer could be giving me yet another symptomatic problem. Fingers crossed this will be the cure.
I did open the valve to see if it was plugged and everything looked clean, so I felt with 2 issues, and neither part being sold separately, just order the unit complete.
I'll let you know next week once it is installed.

 

I had this valve buzzing too, but a new center valve block w/pressure sensor didnt help. Sent back a 'cheap' ebay compressor and waiting for a quality one from Lucky8. Should have gone the quality route 1st when if comes to suspension parts. Fingers crossed!

 

Which compressor are you using ? After you changed the valve block, does the solenoid snap open and closed cleanly again ?
I am using the Hitachi compressor and got my replacement from Rock Auto.

 

After looking through some of this thread I wonder whether you have rebuilt the rear valve block?? One of your significant problems is that the rear settles down when left.
This does imply either a leak somewhere from the central reservoir block to the rear valve block or in the rear block itself. As you have new airbags, that should not be your problem.
It is very simple even though quite fiddly, to remove the valve block and simply dismantle it and clean it. One can buy a kit to replace seals etc but when I did mine, I just cleaned it and it fixed the problem
( rear end settling overnight) and has been perfect for at least 3 years now.
Remember that the fuse for the suspension levelling is best removed while working on it as the suspension automatically tries to level off every 6 hours or so.
The attached .pdf is a good description of the whole system and there are You Tube videos of the valve block rebuild.
Hope this helps.

 

Absolutely a perfect wealth of knowledge in that PDF. Thank you. Now I have an idea where to look for the intake filter.
Regards the rear air valve, it has not been touched and I think it is ok. We did find a leak... and I'm somewhat annoyed at the mechanic I took the car to in the first place to do the work on the car for me.

The air fitting on the right rear air spring is leaking. Not sure how or why, but it is leaking around the threads into the top of the air spring itself. We have removed it twice now and tried to reseal it. Not sure it is even the proper fitting because looking at both sides, they have different fittings.

I need to do a little more investigating there. When we took it out the first time, there was dirt and crud under the taper nylon seal. Thought that was it, but still leaks. The fitting has a very short thread and not really conducive to using Teflon tape, but we tried that and failed again. Will try once more with a special thread sealant I use in the refrigeration industry next time, and if that does not work, maybe a new fitting will be the cure.

Picked up the new center valve block last night and now looking for a chance to dive in and replace that.

Oh the joys of learning new things about old autos. lol .