schranzkt

2004 A8L 4.2L 150k miles

Coolant leak appears on backside of oil pan when car is OFF. Will only leak when coolant reservoir is filled to the MIN line. It leaks until the level drops about 1in below MIN line and stops leaking.

Enough volume pushes coolant out of leaking point. Drivers side appears dry. Leak may be coming from around the backside of engine near passengers side shock tower.

How can i inspect this area? What joint could be leaking? Does anyone have a good diagram of the water system on the 4.2L?

Thank you! Will paypal a small reward to someone who knows the answer!

Junius

First, do you have a 4.2, S8 5.2, or 6.0 W12 engine? If it's the 4.2 (most common variant here in North America) It could be a number of things. It could be the water pump or some small coolant lines. But a commonplace for the 04-06 Audi 4.2 A8's to leak coolant on the passenger side slowly would be the engine oil cooler, which is located (looking from the outside front) on the left side right by the water-cooled alternator. Many people have reported that this part, or rather the plastic pipe that is located inside, gets brittle and eventually breaks, and then leaked slowly over time and usually when parked. But when I had this experience, mine leaked out immediately. Definitely take it to a good independent mechanic to have the system pressurized and to verify where it's coming from. Most likely it is the engine oil cooler pipe, which is not cheap by any means.

schranzkt

4.2L A8.
I think you are right. At first I thought it might be the water cooled alternator but its coming from right above that. which from what I guess would be a pipe related to the oil cooler. I live in Colorado and it is very dry out here so plastics become brittler faster.

I know its not the water pump so I am going to go for the oil cooler. What is the best way to get to this? what needs to be removed? Go in from top or bottom? I am mechanically able to do this just need some direction!

Thanks!!!!!!!!

Junius

I didn't do the work by myself, but from what I remember, my mechanic removed the exhaust manifold on the other side to get to the oil cooler bolts. It is a very tight space indeed.

mishar

The easiest way since those are not $100K cars anymore:

schranzkt

haha hell to the no.

schranzkt

so he went from the top?

I see DIYs that say go in from the bottom, removing the alternator

mishar

You will be sorry.

schranzkt

Youre trying to tell me this replacement sucks huh?

the_duke

I'm glad I haven't had to tackle this issue yet. From everything i've read it's a real pain in the ***. If you use the part linked below it should never happen again.

4.2L Audi/VW Billet Oil Cooler Tube - Gruven Parts