Is it normal for the rear airbag suspension to completely sag after a while of the disco not being powered on?

Have a nasty little ACE leak...don't know where it's coming from. Was wondering how much it would cost to have the whole system done away with and anti-roll bars put in instead?

So I just bought my first Land Rover, a 1999 Disco 2 TD5 not two weeks ago and within two days my ACE warning light came on (after the first right turn), my heater doesn't blow hot air, and my coolant level in my expansion tank dropped significantly. I need help! I am currently a jet mechanic...