I'd recommend a diagnostic check to see if any fault codes flag up.
What colour is the smoke?
It could be an issue with the dpf, egr, injectors or glowplugs but I'm just guessing
I'd recommend a diagnostic check to see if any fault codes flag up.
Most common issues are the suspension airbags leaking or the compressor failing. If you can here the compressor running continually it is often a sign of a leak. I also believe the relay for the compressor can also fail.