audi a4 help
 

hi all can anyone please help, i got an audi a4 2005 new shape 8 months ago and have done nothing but work to it. all services every 8k pads discs timing belt water pump drive belt etc.
3 weeks ago i have put a new aircon compressor and receiver dryer and drive belt and pully. from doing this i noticed my temp gage was going for 70 to 90 never staying at 90. i checked the coolent and it was low so i topped up and all seemed fine. today smoke started flying out of excaust and coolant was near empty. i topped up again and all was fine until 20 mins later the same thing has happened. it seams to be when engine heats up the smoke comes and coolant drops. also the heating has stopped blowing hot air. it is killing me ding all this work. anyone any ideas. could it be head gasket or cracked clyinder or rad leak or tubro.