Question about Suspension Faults and Blowing out the lines

[ryanjl]

2012 LR4 currently sitting at 127,600 miles.

I've been getting some suspension codes that have been popping up every few days.

• C112F-72 (AF) Air spring valve - Mechanical failure - actuator is stuck open
  ( on 26-07-2023 11:10:17 at 205367 km )
• C1130-66 (AF) Air spring air supply - Algorithm based failure - signal has too many transitions/events
  ( on 26-07-2023 11:10:10 at 205367 km )

I plan on doing the suspension test (off-road height, pull the fuse, measure before and after a period of time). Based on what I have read on a search, however, it appears these codes are more often than not related to a valve block.

Compressor was replaced in August 2018 at 73,000 miles. AMK. It's conceivable the compressor could be going bad given it's now 5 years and 54,000 miles old, but maybe not.

I pulled all 3 of my valve blocks back in December 2019 to rebuild them, but the rebuild kit I bought was garbage and only a few of the new seals would work, so the "rebuild" was really just me cleaning out the valve blocks, using most of the old seals, and reinstalling.

I've already got three brand new valve blocks sitting in boxes on my desk. Bought them over the last year intending to do a preventative-style replacement. It just so happens that "preventative" may now be "needed."

My question is this. Is there a good way to blow out the air lines before installing the new valve blocks? In my head, I'm thinking of removing all the valve blocks and then blowing air from the lines from the center valve block location to the front and back ends of the vehicle. Not sure if there's a hangup I haven't thought of, though.

 

[ftillier]

I would think if you disconnected the supply lines at all the air springs, you could hook a household compressor to the inlet of the central valve block to pressurize the system, then use your IID Tool to open all the valves and purge the lines. The only thing I would recommend if you're using a household compressor is having a dehumidifier on the line so you don't introduce moisture in the system.

That said, I don't know that there'd be that much crud in the hoses, perhaps have a look at the valve blocks you remove and then decide?

 

[powershift]

Introducing moisture is a great point. In theory, it was clean when they put it together so unless you get crud in the lines while working on it I'd skip the line flushing. Not only can moisture get in there, if you blow in tiny particles of dirt you can't see that dirt can get into sensitive components and clog a valve. I'd just clean the work area and your tools before cracking the fittings.

 

[ryanjl]

Introducing moisture is a great point. In theory, it was clean when they put it together so unless you get crud in the lines while working on it I'd skip the line flushing. Not only can moisture get in there, if you blow in tiny particles of dirt you can't see that dirt can get into sensitive components and clog a valve. I'd just clean the work area and your tools before cracking the fittings.

Dessicant dust from the compressor dryer gets in the lines. It's normally what fouls the valve blocks. That, and the seals drying up and wearing out over time.

 

[ryanjl]

Update to my suspension codes.

This is embarrassing, but the problem was a leaky tire. I have never found a TPMS sensor I like the look of for my Defender steelies, so I've never run them and have turned the TPMS off. Didn't realize a tire was slowly leaking as my e-rated BFG All Terrains with the thick sidewalls don't really look much different when they are low on tire pressure.

I took the car in for the regular balance and rotate and noticed the codes went away for a few days. Codes came back and I connected the dots and knew it probably had something to do with the tires. Checked pressure and found one that had dropped down to around 30 psi (regularly run 40).

With the tire fixed (screw in the tire) and all aired up, no more suspension codes.

I generally visually inspect the tires every day and pressure check around once a week. Probably should pressure check more often given what I know now, as visual doesn't cut it with these tires.

 

[ftillier]

Super interesting that a low tire would lead to codes. Is the car extending the suspension to compensate and that's why it's getting angry?

 

[ryanjl]

Super interesting that a low tire would lead to codes. Is the car extending the suspension to compensate and that's why it's getting angry?

Well, it was potentially super interesting, but turns out it was wrong. Suspension warning light came back on again today and all the tires are properly aired up. I guess it was just a big coincidence. My theory was that one strut was having to air up a little more than the others, but it's moot now.

I replaced the front valve block a few weeks ago when I replaced my brake rotors. I've got a new rear valve block, a center valve block, and a compressor. Also have two new Arnott rear struts (the fronts were replaced a few years ago).

All things I've collected to have when I need them. Sitting right near 130k miles now, so the rear struts are probably due. Rear valve block and center valve blocks were cleaned out by me in the fall of 2019, but they are old enough where things could be going wrong. Compressor was new at 75k miles. Might save that to last to see if replacing the other things solves the issue, but I guess I'm only 10k miles away from when the first one went bad.

 

[ftillier]

Compressor is a lot easier to change than struts, no? If you have it on hand you could swap it in and see? When you rebuilt your valve blocks, did you put any lube on the o-rings? I cleaned out my front one, didn't end up using the o-ring kit I got because they seemed like the wrong size. I didn't lube anything, but was wondering if I should have used some of my silicone spray.

 

[ryanjl]

Compressor is a lot easier to change than struts, no? If you have it on hand you could swap it in and see? When you rebuilt your valve blocks, did you put any lube on the o-rings? I cleaned out my front one, didn't end up using the o-ring kit I got because they seemed like the wrong size. I didn't lube anything, but was wondering if I should have used some of my silicone spray.

I used silicone spray throughout. Everything seemed to work okay until the last few weeks. Everywhere I search on the codes I'm getting is a situation that was solved with a valve block, so I'm guessing it's probably the rear. That said, the rear air struts look like an easier job than the front, and the front wasn't too tough.

 

[Longtrail]

I also used silicon on my o'rings; I left the car for about three and a half weeks while traveling and didn't notice any appreciable sagging; I have to think the valves are pretty reliable as they're not that complicated in terms of their operation (it's three solenoids). What do you think of the Arnott struts, my 2012 is still running on the originals (approx. 96K miles); I know this is a job that will need doing one day! I suspect the dampers/shocks aren't great.