W212 rear air suspension leak?

[tight fart]

2012 E class estate E350. Every now and again the rear drops, sometimes overnight sometimes it’s fine for 3/4 days.
It goes down level, does that suggest it’s not a bag leak and it’s leaking elsewhere?

[Paddymcc]

I mentioned this on another thread but on my 212 I had a similar leak, particularly one side but eventually both sides would drop if left for any amount of time.

Replaced the offending airbag that I thought was causing the issue but it still dropped over time.

Turned out to be the air line running from the distribution block. It's routed round the spare wheel well and will rub against it over time and cause small pin holes.

Get yourself some soapy water in a spray bottle, undo the plastic cover and spray it on the air lines. I couldnt see any leaks until I gave them a wiggle and spotted the bubbling water.