An ongoing problem each morning both front air suspension heights have dropped an inch or so and pump up within a minute of starting.
Looking at some diagrams shows the plenum under the spare tire having two tubes, one to each front suspension cylinder.
Both have this same rate of leak and wondering what is in common with both sides that would cause this?
Many thanks for any suggestions.

 

Age.

There is nothing else in common between the front struts, other than any allowed outlet of air would be through the compressor, via the solenoid on the reservoir that handles the compressor line.

Having said, "There is nothing else," I'm actually not certain what year went from a height sensor at each front wheel to one height sensor shared by both front struts. Even so, I don't think a height sensor would be the cause of a slow drop.

 

Since certain years share a height sensor as wfooshee said, just one front strut leaking will cause the front to lower together. Easiest thing to check are the top of the strut and air line connections to the struts for leaks. If nothing there is could be the bladder itself or in the lines going to the front struts. Most common would be a strut leaking, but worth checking out the connections first.

 

2005 vdp
Thanks for that, interesting that one height sensor will follow the other and equalize even when parked over night with key removed.
Thinking also if one side goes down doesn't change the height the other side necessary. It's an interesting problem.

 

If your car has two sensors in the front they will lower independently if there is a leak at the strut. Only on models with one front height sensor will they lower together with a leak. Not sure when they went to one sensor, but I know my 06 only has one of the driver side (left side).

 

Well this has been a common problem recently. I had the same issue on my recently purchased XJ, but since it's warmed up recently the suspension has been perfect. No more front end drop... So I got lazy and stopped my research on the issue.

I was going to try and disconnect the fuse controlling the Air suspension and monitor which side drops overnight. Hence the leak.

 

I think we're all guilty of this...we'll worry about it in December Every December/January a bunch of threads pop up for sagging X350s.

 

Your car has 3 ride height sensors. One on driver side and one at each rear wheel. 04 and later x350's went to three height sensors from VIN G26872 and higher. So when one wheel is losing air, the other side will drop as well. Common leak is around the top seal. The rubber dries out, cracks and falls apart. Those who experience dropping when the weather gets colder, but seems to be ok when it warms up, should start planning on replacement. It will only be a matter of time until the car stops rising or the compressor gets overworked and quits.

 

Don B was kind enough to share the following when I took a road trip up the Appalachian Mountains. XJ-8 was parked overnight outside in a very cold night and air suspension was throwing dashboard warnings the next morning. To wit:

"The cold temperature air suspension issues are well-documented. When the temps fall, the volume of air inside the system contracts, resulting in a loss of pressure in the system, including the air bladders and reservoir. The vehicle lowers and the pressure sensor on the valve block tells the ASM that all is not well. The compressor may run, but it usually can't re-pressurize the system in the time allotted by the ASM (120 seconds, I think), and you get the fault warning lamps. On my car, I would often have to start the engine, allow the compressor to run for 120 seconds, shut off the engine, and repeat a second, and sometimes a third time before the compressor could fully pressurize the system. Replacing the compressor piston ring/seal made a big difference".

 

Hello Everyone, I'm just resurrecting my old thread. I never touched the car since my last post since the weather got warmer there were no issues, but the North East cold has returned and so has the overnight front suspension drop (even worse than before). I put the XJ on the lift and sprayed with soapy solution everywhere (air compressor, air bladders, line, etc) and found nothing. Then under hood checked all the air lines, brass fittings, area underneath the air strut electrical connector. soapy solution again and No leaks...

But there must be leaks. After start up the front suspension pumps up, but if very cold and I shut the car off soon after, the front will drop again and I can hear the hissing noise (of an air leak) from both wheels. After warming up the car a bit, the front stays up and I can drive all day no issues.

I'm just checking.. Is there any reason other than the leak for the hissing (leak noise) from the front tires? I find it weird that both air struts went bad together, but maybe it happened. I'm about to buy two front air struts and replace, but love to confirm the leak.

Thanks!

 

You didn't mention checking the air struts themselves, I'll bet that's where the leak is coming from. I'm not expert on the suspension, but I believe if one is leaking the entire front will drop. Especially on the 06+ cars where there is only one ride height sensor for the front suspension. The struts themselves are one of the most common areas to leak, I do know that much.

 

Hello and Thanks. Yes I did spray the air strut (all the connections) and the middle/lowers parts of the strut assembly, but not all the way on the top (from the inside of the wheel opening). It's dropping quickly now so the leaks a substantial when cold. I'm doing an oil change this weekend, so I'll search one more time before I order the air struts. I'd love to find the leaks to confirm.

 

Yea, I hear you. Would be nice to know where the actual problem is, hopefully you can find it. Would you just replace the air struts, or convert to coils? My suspension drops a bit, but only if I leave it for a couple days in the cold so not that bad yet. Will be a big decision when it finally needs attention as I havent heard good thing about Arnott replacement air struts and the OEs are prohibitively expensive.

 

My suspension was like yours.. Dropped a little bit but not too bad... I could of definitely live with it..but now it really drops and having issues keep the front end up in the beginning (when very cold < 32 F) . I pulled a low suspension warning for the 1st time the other day. I had to wait a while for the suspension to finally reach height and hold. I love keeping everything stock, so I'll try my best to stay that route... My LR3 has taught me a LOT of patience with air suspensions.. lol Recently changed an air strut, reservoir tank, and 2 valve blocks. Fixing multiple leaks.

 

Yea, mine has been OK so far. Havent driven the car in a month and it hasnt dropped yet, but I know the say is coming...Still debating on what to do with it. If Arnott replacements had a better record I'd be OK with them, but apparently they're pretty junky these days.

 

Arnotts on both of mine are doing fine

 

After a while, the seals on top of the air springs harden upon ageing and leak more and more, especially when cold.
No other solution than replacing them.
Use the real stuff, Bilstein B4.
Useful video:

 

Mama Mia the air struts expensive!.. Arnotts near 500 and the Bilstein even more. I wish I would have removed all these parts from my totaled old XJ8.

 

Would poor battery affect the air suspension? My 2006MY had been sat for 3 months with a dull battery and was pretty much on the floor when I finally got round to changing the battery, I just used a cheap shop battery (Lion Batteries) and it seems to have returned to normal until this recent UK cold weather snap which has affected it
I do have a new quality battery to go on the car once the EGRs have been replaced and an invisible water leak has been fixed, but should I be concerned about the suspension at this point?

 

Poor battery would not affect the air level other than the point of being unable to run the compressor, and if the battery is that bad, you have other issues. The air suspension module doesn't fight for very long when the car is off, and when the car is on, it shuts down if the results of its commands do not produce the expected results, after throwing a code and showing "Air Suspension Fault" on the dash display.

If the car sags as it sits, there's a leak, maybe several.