SLS airbags going down

[Weekender]

OK this is only a periodic problem. The 2 warning lights stay on a little longer on start up, but go out. The airbags may stay up for all week (sometimes not driven for 2 or so days), then go down once, then be OK again for several days again. The system pumps up very quickly, and no amount of soapy water creates foam on the air bags. The pump and bags are about 4 or 5 years old, so I don't think they are the problem.

any thoughts for this?

Leo

[joel0407]

Just advice. I'm no expert.

Start eliminting parts of the system. You can buy a schrader valve and 4mm pneumatic tube for under 10 bucks. Disconnect and cap the tube from the compressor and connect this either bag. Inflate that bag with a normal tyre pump, leave it and drive it and see what happens.

If that side continues to go down then you have a leaking bag.

If that side stays up and the other side goes down then reconnect the compressor tube and swap sides.

If the first side then goes down but the side you have now swapped to, no longer goes down then you have a problem further up the line and both bags are fine.

There is a valve body in the tray where the compressor is with 3 tubes. The middle tube comes from the compressor/exhaust and the 2 either side goes to the bags. Remove the centre tube and install your tube with the schrader valve. start the car and provide air with a normal tyre pump until the light goes out on the dash. Leave it and drive it and see what happens.

If the bags stay up the problem is further up the line. Reconnect the center tube from the compressor.

From there on you are on your own.

As far as I am aware either of the indivivual left or right valves need to be open for the system to exhaust. The result of this is the exhaust requires both the exhuast valve itself and either a left or right vale opening at the same time for either side to go down. This provides double protection from a leaking valve.

Same goes for inflation. Either the left, right or both valves need to be open at the same time the compressor is running to inflate the bags.

There is a chance that if you do the "connect the 4mm tube with the schrader valve to the middle of the valve block" thing and the leak stops. This could mean one of the valves are leaking and the system is exhausting through the compressor at a slow rate. If this is the case you wont see any foaming from soapy water because the air is leaking out the intake up in the rear tail light.

See here for the 4mm tube and schrader valve thing.
http://www.aulro.com/afvb/discovery-2/181009-my-sls-emergency-spares-kit.html

Happy Days.

[bsperka]

My leaks were a result of the fabric failing. No amount of soapy water showed up a problem with bags in car. Bags out and fully extended - leak as obvious as anything right in the fold area.

[Weekender]

OK, but the mystery is the amount of times the bags stay up - which is almost all the time. But the other day, the bags were deflating as I got out of the car. ten minutes later, I drove home for a few minutes, they have stayed up again all week.

[joel0407]

So follow my process and you'll work out what's causing it. Then you can start to ask why. Right now there are to many variables. It could be a sticking valve, maybe a leaking bag, maybe a cracked line that only leaks when it's in a certain position.

Tell me how long a piece of string is and I'll tell you why your air bags go down sometimes and not others.

Happy Days.

[bsperka]

Tell me how long a piece of string is

Happy Days.

Twice as long as from the middle to one end.... :).

[joel0407]

Well his leak is in the SLS system.

Happy Days. :p

[bsperka]

OK, but the mystery is the amount of times the bags stay up - which is almost all the time. But the other day, the bags were deflating as I got out of the car. ten minutes later, I drove home for a few minutes, they have stayed up again all week.

I had this with my airbags - would stay up in garage, driving etc then drop down. Progressively got worse. As the pump isn't a heavy duty item, if it keeps running, it will bugger up the pump as well. It wasn't a hole,which would leak all the time, but the fabric was slowly delaminating in the fold, until one day it wouldn't go up again, as the pump said noooo.

As Joel0407 says, work at it methodically.His approach is good fault finding as its step by step.

I'd consider taking out each airbag and test it; this should take about 5 to 10 minutes. (Getting it back in correctly may be a PITA though and may take about the same time). Fold it into the correct config helps. Not much pressure required to fully extend the bag and test it for leaks in a bucket of water. I used a bike pump and a bit of drip irrigation pipe taped to the inlet, as I didn't have 4mm at the time.

I've read reports of faulty manifolds, but this was in a new unit, not one that is 4 to 5 years old.

[Pedro_The_Swift]

Remember what holds the car up when playing with the new schrader valves,,

:o:o;)

[joel0407]

Remember what holds the car up when playing with the new schrader valves,,

:o:o;)

I'm pretty concerned getting under the vehicle weather it's just the 4mm tube with a schrader valve or the whole system hooked up. Either way it's just air that can escape at any time. Call me a wuss but I always stick a axle stand under the chassis if I'm anywhere near under the vehicle. It's something I never worried about when there were springs in place.

FYI I'm rebuilding my SLS bit by bit. I'm currently just driving around with the 4mm tube and schrader vales. I put it on level ground and adjusted it. It's only been me in the vehicle but it's been like this for 2 weeks now. I have all the parts, it's just getting the time to get it all installed.

Happy Days

[Pedro_The_Swift]

you really need two(axle stands), per side!
one for the chassis and one for the axle.
uncontrolled movement is the concern--:o

[joel0407]

you really need two(axle stands), per side!
one for the chassis and one for the axle.
uncontrolled movement is the concern--:o

I'm just talking about getting under the vehicle while the wheels are still on and on the ground.

The 4mm tube wont vent air quick enough for it to jump off an axle stand. It still takes a good 5 seconds from normal height to the bump stops. Tested.

I see that as pretty steady but still too fast for me to get out if I have my arm over the axle or something like that.


Happy Days.

[Weekender]

I was going to go off and run my tests as recommended, but just tried the soapy water again - instant foam on the right bag. (had nothing 2 weeks ago) So I purchased a new Dunlop bag from MR and followed all instructions, I seem to have a problem - I don't know if I did it or other, but the bag seems too extended, that is, it seems hardly rolled over the piston and on 3 attempts, I cannot seem to get it to sit right.

any suggestions? I don't think I can roll it bag over the piston....

[Pedro_The_Swift]

release the air, (chassis and axle stands)
bring the chassis and axle closer together, reinstall,

[Weekender]

Thanks for your help.
After a ridiculous amount of time spent yesterday, I popped the bag in in a matter of minutes today - the trick being very incremental with inflation. And yes the instructions do say that - just a bit more touchy than I thought.

I will get it right on the next bag.......

I have attached a picture of the new bag at full length, and a picture of the foaming bag,

Leo

[justinc]

^^ textbook failure.

JC