We had our first real cold snap (18F) and this morning the rear suspension was lower than I've ever seen it. The front is low, but not nearly as low as the back (the top couple inches of the wheels are tucked!). I occasionally get some slow sinking (an inch or two after a week) but nothing like this. It was fine just 12 hours before. Given the computer should auto-level the suspension, I'm really afraid something has gone horribly wrong, like water in the system has frozen and ruptured something. Or a valve block is frozen shut. For peace of mind I'm going to wait to start it up till the temperature clears freezing again.

For those that have had a fully emptied air suspension, does the rear just sit lower than the front naturally? If that's not the case, why would the computer not be able to auto level the system?

 

If you dump the system, the butt end will appear lower. The rear seems to have greater geometry when it comes to travel. If the compressor dryer is saturated, it can freeze up solid. This is a serviceable item that really should be rebuild/replaced every couple years in humid areas. Its possible that moisture in the lines cause a valve block to leak. The system will self-level after 2 hours then again at 6 hours (if I recall). So if there is a big leak and there is no pressure in the reservoir then its possible it tried to level and just dumped out air into the galley. Really you should just be able to fire it up and see what happens. My guess is that with the leak you know you have compiled with very cold temps most of the air contracted.

 

Well, it's fine. Lifted right up to normal height with no fuss and no errors. The compressor did run for a solid couple of minutes though.

I'm just waiting for the error messages to appear about slow to rise to confirm the dryer is blocked and needs replacing. Seems about normal loudness when it runs. Did some leak tests which were inconclusive (all corners dropped about the same amount with the fuses removed). Want to make sure I don't have dryer dust in the system fouling any new valve blocks I replace first (does that make sense?). This was the first time it dropped hard and fast, so thanks for answering the question about normal bump-stop posture!

 

I always recommend replacing the compressor or at least the dryer first. Then after a couple weeks, rebuild/replace the blocks. After all the blocks seem to fail from desiccant powered collecting on the o-rings. So if you just replace the blocks on a system full of powder they will fail in short time again. Also keep in mind that maybe a large-ish sick of dust was on a o-ring then blown off by venting or filling resulting in a "self-repair".

Also check the reservoir for leaks, those tanks can certainly rust out on the ends.

Side note: Just a week or two ago I replaced a compressor on another LR3. We sorta used parts across three used compressors to make one good one. The one he had was a cheap one just over a year and the piston failed. Well with all the parts floating around we put on the wrong dryer and it dumped enough desiccant dust to prevent the vent assembly from seating. So it leaked air out of the system and only go worse. Took it apart and cleaned it up then put a better spare dryer on. Seems fine now. So that dust can be a really pain. I also think it caused premature failure of the bags. They are rubber so having something inside that can pull moisture and cause dry-rot does not seem ideal.

 

Different point of view regarding compressors:

We never bother with replacing just the drier. The original compressors in these were not that great and replacing what few parts are serviceable, in my opinion is just a patch. The newest version of the AMKs have been bullet proof for us. Many shops around us are still sourcing the older style compressors so they don't have to program the suspension module and we have had to replace some of them. We do the new AMK and suspension Software and knock on wood, have yet to have an issue.

 

Replacing the dryer would be the minimum. On a compressor that works there is really no need to replace the whole unit. The dryer can even be rebuilt for under $20 USD. On any other air-ride vehicle I had its considered maintenance, just like the AC dryer actually. Yes, two very different systems. Its just not a part that you typically find on any scheduled system. For my Benz the AC dryer had a seven year recommenced replacement time. As for compressors, I never heard of one being better than the other but I would not be surprised if the AMK is better. We know why Rover switched in the first place. For myself I like to stick with Hitachi because I won't have to update the software. But once I have a GAP tool, doors are open to any possibility.