Being only mildly mechanically inclined and decidedly not a mechanic I figured I'd ask for some opinions on some live values I am getting after rebuilding my compressor. Quick rundown. I was getting gallery not venting fault so decided to rebuild the compressor to see if that would help. Compressor partially rebuilt, didn't touch the piston area at all. Everything is back together suspension back operational, took a little while to refill everything with air and my compressor temp was getting high so I actually let it cool a couple times to get there. Today is 90+ degrees and I wasn't really sure what the temp limit on the compressor would be, assuming it would shut itself off if it got too hot.

Anyhow, on to the questions. decided to take it for a test drive and ran my BT Gap Tool while out to see what was happening with the EAS. I put up live values of suspension calibration and actual height along with gallery pressure and compressor temperature. You need to find an empty road to be able to watch the values as you drive or have a helper. Anyhow, my gallery pressure was fluctuating quite a bit. It would increase with the compressor being on. I could assume the compressor was running based on pressure rising and temperature rising. Gallery pressure would rise to about 200psi and compressor temp would rise to as high as 270F. At which point the compressor would turn off and the gallery would begin to drop. It would drop within a few minutes to the mid 80s psi and even a few times to as low as 35psi. The compressor would then be cooling and drop just below 200F. Then compressor would kick back on, psi rises back up, compressor temp rises, etc. So on and so forth. Not knowing exactly how this system should function properly I'm wondering. Is this normal? During this time the ride height remains very steady, right where it is calibrated and only varies +/- an inch during driving on a flat smooth road.

I guess I don't have a gallery not venting issue anymore but I'm feeling like the compressor is running too much and the gallery should be holding a certain pressure. Thoughts from someone with more experience? Hopefully this thread will also help someone else as there seems to be a constant stream of EAS related questions.
Cheers.

 

And I'll note that the vehicle does eventually drop over time. Takes about a week of sitting.

And, when I returned I turned off the vehicle and just sat and watched the values. Gallery pressure slowly dropped over about 5 minutes to settle out at about 15psi.

 

Sounds like you have a leak.

Your pressure is a bit low, but that could simply be a pressure sensor out of spec. Your operating temperature seems okay. Under normal conditions you should not overheat and I avoid doing so at all costs. I think a software update, which you may already have, actually reduced max operating temperature.

The system is pretty simple. You have a compressor to build up air pressure, a reservoir to hold some extra air to assist in rapid height changes and a "gallery" of air lines. The reservoir is sealed from teh system at the center valve block. That is located just in front of the compressor. That valve block also contains a pressure sensor for the gallery (NOT the reservoir).

^ All that you probably know.

When operating normally, the compressor engages when it detects that a height change is required to lift upwards. This is caused by user input at the switch OR automatically if the vehicle needs to make an adjustment, which could be caused by a leak in a strut. So normally you get in and start it up. Typically the compressor fires up because its not unusual for a slight adjacent being needed form sitting. It should not operate for long because in a working system there would be plenty of reservoir air to assist with the very minor height change. And the compressor is really just topping off the reservoir after the heights are in spec. 10-20 seconds, max.

Before the compressor operates, it must vent the gallery. This is normally dont right after compressor operation, actually. So you normally hear it run for a while then blow off. A compressor fart. This is to back off some pressure so when it fires up next time the into piston is not fighting high gallery pressure. If gallery pressure is still too high before it needs to run, it may far before also.

The gallery is not air tight. It does not need to be for the reasons stated above. In a new system gallery pressure may hold for a long time but it will still likely bleed down. I know of no LR3 that can hold gallery pressure perfectly forever.

So now going back to your specific issues, if the compressor is running a lot that generally means there are height changes being requested. Gallery pressure along does not dictate when the compressor runs, its not quite like a shop compressor where pressure is "monitored" and the compressor operates to maintain that PSI. (I used to think this is how it ran originally, now I know it does not). So you can basically have a truck driving with no leaks but a gallery pressure of 0 and he compressor should not fire up. So I would have to say that if yours is cycling a lot, you have a leak at a strut or valve block where the strut is dumping air into the every leaking gallery.

 

Ok, after a bit of uncomfortable yoga I have found the issue. The answer to the question is no, the gallery pressure should not go up and down like that. I have a leak at the top of the desiccant container in the Blue (system feed side). I do not think I had this issue before the rebuild so there is a chance that maybe I have damaged the tube or the connector that is in the top of the desiccant container. I have removed and re-inserted the tube a bunch of times and there is still a leak. Going to order a new one of each and make the repair. Really excited to pull that dang compressor out again...

 

Great care must be taken when removing the lines. You gently and every so slightly push the air line inwards WITH the collet. As one. Then when the collet has bottomed out, you gently pull the line out while keeping the collet all the way in. If you let the collet slip then the metal catches inside scratch the line. Now the line has defects that damage the o-ring inside the collet. So they are pretty dang easy to damage. You can try cutting a bit of the line off but some have stop moulded in and some lines are not long enough to cut. But I have cut a few to make them seal better.

You should also consider a valve block rebuild kit. They are on eBay for about $22 and contain all the o-rings for the front, center and rear valve blocks. The desiccant gets on the o-rings which results in leaks.

 

Cheers.
I seem to have damaged the outlet of the desiccant container as I've trimmed the line and still leaking. Guess I'll have to wait for the new one to arrive. Regarding the on and off of the compressor. A better understanding of what makes it cycle would certainly help understand why it is running as much as it does. Suggestions on a live value to watch to see what the trigger is? I've been watching gallery pressure and compressor temperature and there is no real consistency on when the pump turns on other than, when the gallery is quite low and when the motor is quite hot. Gallery pressure has raised to a max of 225psi. Wonder what pressure it generally should stop at if that is indeed why it would stop.

 

Well the other problem is the dryer caps can crack between the lines. That happens with time, after years of use. But people tend to but the metal caps from eBay. Never have that issue again and you will have new fittings.

Max gallery pressure is 250psi I believe. But there is a window it operates in. So if you are reaching 225 you are probably okay. The triggers I mentioned above.

 

Always appreciative of your help. I guess I was asking what, if anything could be monitored to see what is calling for a height change, like which corner or height sensor. There doesn't seem to be a height sensor monitor in the live values. The compressor comes on and off just sitting in the driveway with the vehicle running. Leaving the vehicle overnight results in zero change in heights from center wheel to wheel well. So I'm feeling like there is no leak in an airbag. Hoping to be able to diagnose better after all the gallery air doesn't just pour out of the gallery the second the compressor stops.

 

You should be able to read the height sensor values with the GAP tool. A valve block can be leaking, but that would mean it would leak overnight too. I don't think there is a way to observe the EAS system commands without maybe some fancy Rover software.

 

Update- Replaced desiccant container with new one and a new piping kit. Problems solved and EAS currently working as it should.