Car was overheating at first and coolant was spilling on the ground but didn't know where it was coming from. Did not change theromstat but changed alternator and tensioner belt, sereintein belt. Drove it to the store and back once and a while. One day it started overheating a lot and shut off and wouldnt start again. We change spark plugs and checked coils. Now car still wont start, it turns but not ignition. When you fill the coolant tank it fills and then drains and empties but does not spill on the ground anymore. Slight collant in the throttle body. Please help, can no figure it out. The car is a 1999.5 audi A4 1.8t. Thank you

You fill the coolant tank and it drains with no coolant on the ground? check to see if your oil is milky. hopefully you are not filling your oil pan with coolant

did it start smoking after it shut off? maybe your engine is done?

Did you hear knocking? White smoke? Pull the spark plugs, and get a look down there with a light, do you see coolant?