My SLS is funky !

**Fluids** · 1st April 2010, 03:38 PM

So my right rear air bag seems to want to deflate of its own accord. Sometimes it doesn't ... for days, or weeks on end, then for no apparent reason it's down ... but never to the bump stop.

Even though I have a problem on the right only, I have checked the left side as a matter of course as well.

1 - I have soaped the bag all over and there is definitley no leaks on the bag anywhere.

2 - I have checked the union nut on the top of the bag. I have soaped the union nut. Not leaking.

3 - I have nipped up the union nut at the compressor valve block. I have soaped the union nut. Not leaking.

4 - I have traced out the air lines to the rear bags. No leaks, chaffing or scuffing anywhere I can see. Not leaking.

5 - From std ride height to off-road height takes 13sec's. Once in offroad height, it NEVER sags. Not ever.

6 - If i open the back door, and leave it open for a few minutes, the back settles down like it would using the suspension plip ... always rhs faster than the left.

7 - I have noticed recently, braking before a speed hump, then crossing the speed hump, seems like the back rhs bump stop is bottoming out, feels low in the rse but levels off again pretty quickly.

After going round on this, and searching the forum on SLS issues, I have found no faults.

If it was a leaking bag, it would leak consistantly. Mine appears not to ? Sometimes you can literally watch it go down over 10-15 sec's ... then raise up again in 10-15 sec's and NOT droop again ... ??

I plugged the Nanocom in and checked the SLS ride height readings. Seems the set value, shows the same for both sides (say 187/187), but when I read the real time values, the lhs will show 187, but the rhs (problem side) will show less (like 137, or 145, or similar). I tried raisning the rhs manually with the nanocom, and it raises, but the readings for the lhs show a raise too ... thinking I could readjust one side only ... seems not ... I could never get the rhs to read the same as the lhs. If I raise it too far, it just blows off and airs down the rhs again.

So, after all that, I deduce that my rhs suspension height sensor is failing. I disconnected the wiring loom, and contact cleanerd the plug, and re-assembled ... no change. The rhs sensor reading is always lower than the lhs, and the set value for both sides seems to always be equal to whatever the lhs set reading shows on the nanocom.

Ride height sensor failure ?? .... and if so, should they be replaced as pairs ?

Going to have to live with it over Easter (I'm on the 4WD Action Discovery Day drive up around Lithgow testing the new D4). It will be OK I reckon, but I think it's slowly getting worse. Rides OK on the highway and doesn't sag.

Let the collective wisdom flow ... please

Kev..

**biggin** · 1st April 2010, 06:20 PM

I'm not trying to be smart, but I'm pretty sure you need a new airbag!

**Fluids** · 1st April 2010, 09:05 PM

I knew it ... I knew it ... I just bloody knew it .... some goose is gonna reply and say ... "you need a new airbag"

Just gotta love this place

Thanks for the advice ... I'll check and get back to you

Kev..

PS ... no offence taken

**jwb** · 1st April 2010, 10:30 PM

all the symptoms of a porous air bag. replace them or you'll be up for a compressor as well....

**strangy** · 1st April 2010, 10:33 PM

Try disconnecting the sensor arm and have an assistant wriggle the arm at the sensor and also move it through the range while you monitor the outputs. Have the compressor isolated and the vehicle supported on stands.
Any skips in the readings may indicate a deeper issue with the sensor. You dont have to replace in pairs.

Assuming the bag is definitely not at fault.
The description of watching it go down and up a few times before settling and not changing when in off road mode, IMO is indicative of a sensor OR sticking/ failing solenoid valve or seals. No seal kit is available and nothing aftermarket (that I could find anyway) will interchange. You can pull the solenoid apart and replace the body o-ring, this is highly unlikely to be at fault.

As an aside, are these the original bags? What brand bags are you running? Now if you have newer bags fitted and these are from company in the US, I would not be at all surprised if the bag was the fault, leaking around the retaining ring.

Cheers

**gazk** · 1st April 2010, 11:50 PM

Originally Posted by jwb

all the symptoms of a porous air bag. replace them or you'll be up for a compressor as well....

Concur, helped a friend sort his out a few months back - turned out to be a porous bag. (The leaky part was about the size of 20c) It was very hard to detect and the sagging on one side happened on and off for a few weeks before the leak was detected and a new bag fitted. Last week his compressor failed completely - fitted a replacement thanks to Bundalene. The replacement is much quieter than the old one was before it failed.
regards

**Fluids** · 2nd April 2010, 10:32 AM

Thanks Strangy! That's an excellent idea about disconnecting the arm and checking it's operation manually with an assistant & the nanocom.

Yes, they are the original air bags. Just on 6yrs old. I appreciate the fact that they can fail at this age. I've seen the post about those new bags that leak around the sealing ring ... won't be using those at replacement time

The bags fitted are Conitech, or something like that.

JWB - I even used a washer soaked in a high concentration detergent mix and swabbed it slowly all over the bag in off road mode to look for air leaks. None found.

Gary - I'm pretty sure the air bag is OK, and Strangy's pretty much confirming my diagnosis ... ride height sensor. I have been fooling around with this for almost 12 months now trying to diagnose ever since we bought the D2 ... you'd think a leaking air bag would get progressivley worse over this time ... it hasn't changed it's behaviour ... when people point it out, we just say "oh, it's just gone to sleep!"

Now, the Disco's been parked overnight, about 12hrs. It's still sitting level. I just went down stairs, unlocked it, and have opened the back door ... about 15min ago ... just went and checked .... still sitting level. I then closed the rear door, started the Disco, closed the drivers door and checked to see if it adjusted the ride height ... nope. Sat where it was. I stopped it, and then opened the back door (apparently the SLS system remains active up to maybe 15min's after ignition is turned off) .... 15min later ... still hasn't changed ... BUGGER ... this is like trying to hit a mooving target!

... and the sagga & searching continues.
Kev..
Kev..

**kenl** · 2nd April 2010, 12:12 PM

I have had EXACTLY the same problem for the last 8 months or so. It seems to be somehow related to opening the rear passenger door and or the rear rear door?? I have however ordered a set of airbags from Paddock spares as they have them on special, so I will let you know how it goes. I expect to get them in the mail ant day now.. I've also bought a D4, so the old girl doesn't get much of a look in these days!!

**sniegy** · 2nd April 2010, 12:29 PM

Kev,
The word you are after is "AIR SPRING"

Even when the vehicle's rear end is in off road height, the top portion of the air spring is still folded & cannot be tested, this is where a lot of them fail due to the rubbing & in due course fail.

HTH.
Cheers

**justinc** · 2nd April 2010, 03:32 PM

Just a word about testing these things, ALWAYS when using soapy water etc get someone to stand or bounce up and down on the tow bar or rear bumper and watch the bag THEN. The leaks will be where the bag folds under, opening up the fabric allowing air to escape. Just spraying it and watching it on level ground probably won't show anything. ALSO, there are possibilties of an air leak in one of the lines as they can rub through on the upper rear crossmember etc, but that usually is a constant leak that never 'repairs' itself.

99% of the time, the RH side will fail first

My guess is YOU NEED A NEW AIR SPRING

JC

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