jet2 737's dodgy engines??

Whilst at BFS/EGAA on Boxing Day Jet2 Maint. were out in full force around the engines of the 2 737s they had which are based i think.

On one 737 (red tail) they fiddled with right side engine and when it eventually started and pushed and started engine lots of white smoke came out (oil change?)

The other one didnt leave whilst i was at the airport but alot of Jet2 cars/vans and at least 10 people (i assume 2 baggage and 1 refueler) around the aircraft in yellow jackets. They seemed to be around the right engine.