This is my first post here but, this seems to be the place to get good help on the A4. Thank you for any help you can give me.
I am helping my college son get his car going again, so I will give the back ground upto this point. His buddy was driving and hit a big bump in the road and cracked the oil pan, both lower and upper. After many hours of replacing them, timing belt & pullys, water pump, thermostat & housing, it is back together and running fine. It now has a fairly big leak behind the motor somewhere, that I am trying to locate. It is dripping mostly off the flywheel bellhousing area right in the middle. I removed the nipple to the reservior per the sticky, on the back crossover last night (it was not tight) that had a lot of antifreeze buildup around it. I teflon taped it and put it back together using the same washer (not sure teflon tape will even help) and something is still leaking today after you shut the motor off, it probably lost 2-3 oz this morning. The car was probably leaking before, but I think something may have been bumped when lifting the motor to replace the upper oil pan. I need help locating where the leak is at and how to fix it.
If it is the Crossover how do you go about changing the O-rings. It looks like a hose from the crossover going to the tunnel (heater maybe?) maybe leaking some also. Everything is so tight back there, you can't hardly see and definitely can't get a hand or tool back there to do much. Do you drop the motor/subframe to get clearence or have to pull everthing forward? Is there other coolant leak spot that I can look for, or better way to locate this leak?
Thanks for any help! Rockie

 

Ok after putting the car on jack stands and placing paper towels in different locations, I found what I think is the culpret. It appears that the thermostat is leaking on the back side and running down the intake manifold to the back of the motor, which explains why it doesn't appear to leak when sitting still and running. It looks like there is a ledge on the back side of the manifold, and it can hold a couple of oz of fluid before it spills over. It also doesn't seem to really leak, until it gets hot and builds pressure. I will be pulling the thermostat tonight and taking a look at the oring. Maybe we nicked it when installing the new one. More to follow.

 

FYI, Pulled the thermostat out last night and the oring was torn. I put the oring from the old thermostat on and put it back together. That's what happens when you try to teach your kids how to fix their car and give them some leeway to do it. It looks like it's not leaking anymore. That nipple from the reservior to the crossover was definitely leaking before though, because when I was looking for this leak, I noticed antifreeze buildup about 1/2" on the bottom of the crossover from the bottom of the car.

 

that crossover pipe is also a known culprit for leaks

 

Thanks, I read that, and that is where I thought it was coming from. It looks like a real pain to change the o-rings for it also, but then again, what isn't a pain on this car. For being a supposed better engineered car, I see many things that leave me feeling that it is just a more expensive car not better made. When fixing the leak on the nipple I broke the hose for the PCV to the valve cover. What a piece of crap that thing is!
Sorry for babbling, thanks for the tip.