Discovery II | SLS Valve body issue?

I've got an issue with my SLS system and I think it may be an issue with the valve body. Here's the symptom:
Occasionally (happened yesterday), both bags will deflate after shut-down. Sometimes, I can audibly hear the air release after the vehicle has stopped. It seems as if the customary pressure relief / stabilisation that occurs about 45 seconds after shut-off fails to seal properly. Under 'normal' circumstances, the bags will hold pressure and height for +2 weeks without any sag. Upon start-up + customary delay, the bags re inflate normally.

Question: Is it possible to 'clean' or re-build the valve body? I checked the filter earlier this fall. The outer foam bit had disintegrated, but the inner felt bit appears fairly clean. Our prior home was in western Africa, and surely Bob has seen some dust in his day. I've not dropped the compressor box yet. Alternately, is it possible that I have a dirty door contact switch - and its sending some false signal to the controlling computer? There aren't any errors showing up on a NanoCom.

Question 2: Is it normal for the SLS to move the bags frequently while under motion? I can tell, that coming to a stop in town, that the bags will commonly adjust while I'm stopped at a light. I would have guessed that the logic in the controlling computer would include a delay - avoiding constant adjustments while under motion.

Thanks, in advance, for any input.
Detroit Disco

Replace both bags cos most probably you have a bag leak and the best is to have them both new at the ame time, they have the ability to intermittently seal themselves and continuing without the bags being 100% ruled out the compressor might die too

You can certainly take the valves apart to some extent, I managed to dislodge mine trying to wedge the cover back over the compressor when it wasn’t lined up properly. Disconnected and unbolted it, separated the two parts, reseated the o rings and put it all back together.

Sierrafery + Adam,
Thank-you for the responses.

I'm hoping to drop the compressor box this weekend and have a look at the valve assembly. Likewise, I can put some soapy water on the bags and see how they're doing when placed in the 'high' position. Based upon service records, I think the bags are about 5 years old - so surely possible that they're aging out.

Several brands of bags are available - are the Contitech acceptable quality? I know that in the U.S. Arnott makes bags that fit - and they appear to be decent quality as well.

Again, thank-you for the input. I'll keep you posted on what I find.
Detroit

TBH, with 5 year old air springs, I wouldn't even bother with the soapy water, I'd change them first as last. As @sierrafery has said, once you change them you'll know that they're 100% so you can rule them out of any further fault finding.
Experience of the forum does suggest that the bags last about 5 to 7 years.

Contitech bags are in use in the UK, as are Dunlops, as to what's available in your homeland, I couldn't possibly comment.

If we’re talking about the same valve block it’s only held in by a couple of bolts, no need to drop the compressor box unless you want to. The other advice has come from those far more experienced in the D2 than I but I would agree, bags first then start considering what else it could be. I don’t intend on leaving mine on any more than 2 years or so before replacing again - assuming I have the car that long.

Update + Close-out:
I replaced both bags with Contitech parts and it resolved the intermittent sinking issue. The driver's side bag had a very subtle leak that only occurred when the Disco was parked on a slope. When I removed the bags it became pretty obvious that the driver's side had perished.

Glad you're sorted. Were they the push in type connectors for the air line?. Mine are both screw types at present.
Griff

To respond to Griff's note - for other's use, yes, the Contitech bags came with 'push' style connectors. My tips:
- be frugal cutting the ferule; there's not much line slack
- clean the line with some alcohol / brake cleaner. it can't be good to have a contaminated line in such a 'mysterious' connection.
- make sure the line end is cleanly cut and line remains circular
My connections went well and have held just fine - but I was pretty skeptical when pushing them in for the first time.
Andrew

Hi Andrew,
A late reply is better than no reply
Cheers,
Griff