i have a 2003 Audi A4 1.8t 2 wheel drive,my thing is i put a new thermostat and water pump,timing gear.now when it sits and idles its fine.But when i drive it down the road it starts blowing antifreze out of the bottom of the plastic jug.What the problem?

 

just a guess,the reservoir could have a light crack in it.when it warms up, it expands and allows for the coolant to escape. it wouldnt be the first time ive heard of a bad reservoir

 

^^^^^
Could be this

Did you bleed the air from the cooling system after you did the timing job? You could have passed a bubble