I have a 2000 Discovery that has developed a hiccup. The rear suspension doesn't like to stay inflated. It sounds like air leaking when it is parked. A seal? It rises to the proper level, but then deflates. Looking for advice. (It has the off road optional switch to raise the suspension for off road)

 

Welcome aboard Fin !

Your 00' Disco II has SLS ( self leveling suspension )[ Added to FAQ ]
Use A spray bottle with soapy water and spray all around the rear air bags. You should see bubbling. Replacement of the bubbling part is required.