Almost certainly...
An extremley knowledgable chap on hear (Datatek) who seems to know almost all things P38 has passed on several times a very simple check to see if the EAS Compressor is pullings its weight.....
- Open the Plastic lid covering the EAS Compressor and valve block
- Un-bolt the compressor from its rubber mounts
- Un-do the Blue plastic output airline from the compressor
- Either turn the Vehcile engine on or if you have some cable, run the compressor direct from the battery
- Place thumb over the air outlet port, a good compressor should make it nigh on impossible to seat the thumb due to air pressure (don't panic it is not going to take your thumb off as it is not a high volume pump just high pressure)
- If you can put your thumb over the hole with little resistance, the piston seal is knackered or the cylinder bore is scored.
Luckily all is not lost, you can get replacement Teflon seals and new cylinder liner from Fleabay for less than £20.
A recon pump will be upwards of £125-150.
If the system, once it is up, sinks over night, I would look at the suspension air bags, as they may be leaking, they usually have a life of around 6 years (70-80k miles) so may well be worth checking out, as if you replace the compressor parts, and it is going to have to continually run to replace leaking air, it isn't go to last too long before it goes again.
If after carrying out the above 'Thumb' check and the compressor is working well with good pressure, look for leaks in the air bags, or valve block....some valves in the block don't seat propoerly due to a tiny amount of dirt caught within.....
Good luck and let us know how you get on.