I have a 99.5 A4 and the transmission cooler lines are leaking where the hard lines go into the radiator. (I also have a 2001 with a bad tranny that I am using for parts).

Yesterday, I drained both radiators and this is what I found...On my car that I am driving, when I opened the drain, only about an ounce came out then the petcock clogged. I shot some compressed air in there and got it to drain and the water/antifreeze that came out looks like used oil.

There is a little back story to this, the guy I got the car from was driving it with a massive water pump leak, so it was being driven without water at all. I got the water pump/timing belt replaced and have driven it about 1000 miles without issue, but I didn't know how nasty the inside of the engine was until now.

The picture shows a sample of the antifreeze drained from my donor car and my 99.

I am in the process of flushing the engine with water, then I am going to install the radiator from my donor car.

 

I have flushed the system 4 times, from right to left are samples of the coolant from each flush (with plain water). I think I will install the new radiator and flush it with water/G12 one more time.

 

I flushed the system with water 4 times. Each bottle from right to left represents the first sample of fluid after reaching operating temperatures. Here is my question, Do you think the radiator is shot and needs replaced or do you think it is still usable?

thanks,
Gary

 

You should pressure test your radiator. If it fails consider yourself lucky because if the radiator is good then you need to replace your headgasket.