Forum:
Hi there
I could do with some more advice (...again...).Over the last few days I encountered quite a blue cloud behind my trak when setting off in 1st gear (I mention that because for some strange reason it only seems to happen in 1st...) even on a hot engine.It seems to stop immediately once we are rolling.I also seem to notice a rather disturbing rattling noise from the engine at the same time.Has anybody got any ideas??????? 
When was the oil and filter
When was the oil and filter changed?
I suggest you renew both oil and filter. Make certain you use oil for diesel engines and not oil for petrol heads. Use a thicker oil than recommended - get advice from a good motor shop. Possibly add a good oil-additive. Some additives are designed to stop blue smoke.
Engine oil is escaping between the cylinder rings and into the cylinders. There it gets burned and emerges as blue smoke. Oils escapes because its age/use has destroyed its viscosity. Alternatively the cylinder bore/cylinder rings have become worn. The rattle is probably due to cylinder wear. If its a 'knocking' then the big or little ends are worn and damage done. However if the engine oil is worn thin, then the engine will rattle - get the oil changed asap.
Yes its more noticable in 1st gear because the engine has probably been ticking over.