tecra

3 month ago my 2001 2.8 avant tiptronic developed a pretty bad oil leak when I was driving across the states. It would lose 1 liter of oil in 600 miles. I sent it in to a highly regarded audi shop and it was diagnosed as a upper oil pan seal leak. Driver side valve cover was fine, passenger side just done prior to the trip. Front of the engine was clean and dry. Cam adjuster seals were fine. No oil on the catalytic converter close to the exhaust manifold. The leak was seen where the transmission meets the engine. When the shop replaced the upper oil pan they checked the rear main seal. It was not leaking.

Anyway, after the upper oil pan seal was redone, I drove it for a while and the leak was back. The shop cleaned up the underbody and test drove it. And then they discovered that upper oil pan seal is leaking again. They honored warranty and redid the upper oil pan gasket. But when they took the oil pan off they couldn't find anything wrong with it. The seal was fine. They then double checked the rear main seal again. It was not leaking. Out of clues they reinstalled upper oil pan and asked me to keep an eye on it.

As you may expect, the oil leak is still there. I jacked up the car and took a close look. It is the same place. I can see oil around the white upper oil pan sealant.

Relevant history on this: car loses oil quickly when driven fast for extended periods (70 mph for hours, loses 1 liter of oil between services 3k miles). No exhaust smoke. Suction pump replaced. Green check valve original. Idles and runs smoothly. Recently developed a front passenger side differential leak, but I think that might be a separate issue.

So guys, what should I do next? Thanks in advance.

4Driver4

Cam seals? Breather? Cam plugs?

tecra

The back of the engine is a bit oily, but doesn't seem like oil is pouring out. I'll double check to see if it smokes upon cold start. The shop stated that cam stuff is not likely the cause, but they could be wrong.

By breather you mean breather tubes? That'll be the next item on the list.

If no cause can be found, I may have to consider "snake oil" option

4Driver4

Snake oil option? Best of luck with that, especially with a leak like you have.

Wash the back of the engine down and run the car. This seems like a simple case of misdiagnosing the problem.