i aksed a few weeks ago about what could possibly be leaking coolant and i got a few options to look into. i did notice that the reservoir tank did seem to have a few drops coming from it but i dont think that is really the issue. I installed the APR snub mount last night and i had all the covers underneath off and i noticed that it seems to be running down the sides of the tranny but mostly on the drivers side. I didnt seem to notice the after pump anywhere so im still not sure if thats it or not. oh and i love the snub mount by the way, its amamzing

 

I would look into the expansion tank, if you see drops coming from it why wouldn't you replace it?
Once they start leaking a little bit its only a matter of time until they start leaking worse so keep an eye on it.

 

The coolant lines that connect to a tee for the turbos are right on back basicaly above where the tranny mates to engine, they could be leaking. Each turbo feed line hooks to a T which the third hose is connected to afterrun pump

 

i plan on replacing the coolant tank, i just noticed it last night so i havent been able to yet. i will look into those lines, its just so damn hard to see up in there. i might try to get it on a lift next week and take a peak

 

I have the same leak you are describing, im not too sure what the thing is called or what it does because i am still a new owner but the part tends to leak on s4's often. If you look underneath your intake manifold you will see what im talking about.

 

i finally found where the leak is coming from and it looks like its going to be a bitch to get to. but the trouble spot is a coolant T on the backside if the motor where it looks like two lines connect and go into the block/head. i am going to try squeezing down in there and replacing teh clamp to see if that stops it, and if not ill replace the hose and clamp and go from there. Is that a common problem area for S4's?