ive got a hilti te22 and its been playing up lately due to a broken wire in the lead.whilst i was mending this i decided to take the small cover (50mm x 30mm approx)on top of the drill which has 2 screws in it off.once open you can see a chamber with some sort of rotary arm in there.my question is, should this chamber have some sort of oil in it,as mine seems to empty.the cover has a rubber seal which indicates the chamber should have oil.
I would just put it in for a service/repair. Sounds like it needs it. If you are dealing with a bit of hilti kit I wouldnt trust any answers off here.