Hi all, after searching many sls related topics, most pertaining to airbag, height sensor, SLABS, compressor issues, I am left unanswered... Just yesterday I noticed the ride getting softer and softer. The back end had not noticeably sagged. I pressed the off road button and the light kept flashing with no lift occurring.

I have determined the fault lies with pipework. The bags hold air, the compressor runs, but I can hear air escaping near the back of the vehicle every time the compressor runs. My understanding of the system is that the two bags are supplied individually from the valve block in the compressor housing. Therefore I cannot work out why neither side will inflate, as the odds of having suddenly split both air lines simultaneously is very slim.
How can I trace the fault without injuring myself to death? Does anyone have a schematic showing actual routing of the air lines around the rear axle area?

Are you sure that the air is not coming from the compressor area?... the exhaust valve used to make tricks there, but if you are certain that the air is coming from the back remove the LH lamp and listen there at the SLS filter...if you hear the air there it means that you need a seal kit to fix the compressor cos the piston seal in it is gone and it creates back pressure to the intake... i doubt that it's a pipe leak as you described it and it is becoming soft slowly not dropping to the bumps

IMO that's what you need http://www.island-4x4.co.uk/suspens...discovery-rqg100041-rqg100041kit-p-27891.html

I think I understand a little bit more about the system then. So what you are suggesting is that leaking pipework will result in near immediate collapse of the airbags, therefore ALL the valving is at the compressor end? I will remove the light as you suggested when it stops raining and test again.

i dont have a diagram of the pipe disposal but here is how the compressor assy is built

I have the compressor out of the car and I have bench tested it. There is air coming out of the supply line to the valve block, but it it is weak. This could be because there is also air coming out of the exhaust valve. Does the exhaust valve default to open when de-powered? If not I guess compressor seals, otherwise I may have to investigate the exhaust vlave.

the exhaust valve is normally closed, it's not supposed to let air out without deflation command from the ECU, there is the other mechanical pressure limiting valve too which can make tricks... but you are on the right track anyway, IMO the problem is there somewhere, one of those seals(that larger o-ring) is for the... better get that repair kit and overhaul the compressor then try again, unless there's a crack somewhere

Thank you for the tips and advice. I dismantled the pump, removed the exhaust valve, disassembled the pressure relief valve and cleaned and dried everything. The culprit was the pressure relief valve which was not seating. I have cleaned the prv and reassembled. It has maybe 1℅ leakage now. I have refitted the compressor to the car and it pumped back up to normal height within a minute.

Can you buy a new seal disc and o ring for the relief valve?

the only kit i know of is that fom the link i gave you