Affecting: [C4 Picasso C4 Grand Picasso and Expert & Dispatch & Scudo Vans]
There is much talk about this problem. No doubt you have already trawled the net for a glimmer of hope - like many others, to little avail.
The pneumatic system as employed by PSA on these vehicles is sadly fraught with problems. Having forked out for airsprings three times at the dealer's in 5 years and then being presented with a bill to replace the compressor was just the final straw for one of our spring conversion customers. PSA honoured the warranty on vehicles of a certain age and did make a contribution on later vehicles. Alas, that has come to an end now and you are basically on your own.
Anyway, like knights in (grubby) armour Eurocarcare charge to the rescue with a foolproof conventional spring conversion. To date we have converted well over 500 very sad Citroen Peugeot and Fiat owners to happy motorists again. Our kits can be installed quickly and easily with little more than a spring compressor.
For C4 range: https://www.eurocarcare.net/rear-suspension/ecc5102gn-coil-spring-conversion-kit.html
For Van range: https://www.eurocarcare.net/rear-suspension/5102gq-van-coil-spring-conversion-kit.html