I know this is common among Discos ('01 Discovery).
I have it now ... rear pasenger side will sit down when off - if you start the engine and run it a while with all doors closed - it has been coming up.
But lately, even after coming up it starts losing air and losing the suspension ride and starts bouncing as i am driving along.
Any ideas ? has anyone had this issue and how did you fix ?

 

You can do a search here on the Disco froum, there are MANY posts related to this.

 

get a spring conversion kit

 

Above reply is best, b/c these are an "expendable" like tires and brakes. I couldn't convert to springs because I have ACE - active cornering enhancement - on mine. If you do too, contact Arnott Industries in Florida (google) and get one (or two better) replacements at around $125 each. Install is easy if you're mechanical and have a lift or floor jack DiY, otherwise shouldn't be alot at a suspension or tire place like Mavis. Sorry for the name dropping, but I believe people who stand by their products/services deserve mention.

 

If you like the SLS like many of us then go order a set of new Arnott Industries air bags, less money then factory, better bags and come with a lifetime warranty.
They take a 1/2 or so to replace and you'll be set.