I was standing by my car and heard a loud release of air from the back tire area. Now I have a car too low message.

I’m assuming there are air shocks in the back, (I just had a front one blow up)

I’m wondering if this is a leak that can be repaired or do I need to replace the air shock.

 

R M T rebuilds your shocks, or trades you another set of rebuilt shocks for yours.
I sent the set of fronts in to be rebuilt, then just swapped them out.
That set is still setting in my garage, in boxes ready to ship, if their ever needed.

 

From your description, I would think one of the rear air spring diaphragms has given way. It is possible to replace these as Wingrider says. It'll be a lot cheaper than a new air spring unit from Bilstein.

https://rebuildmastertech.com/jaguar...rt-suspension/

They also seem to have the airline fittings too.