engine bay leak

I'm still chasing my leak. I cleaned the engine with a citris based cleaner. the leak is slowly showing up. There is a hose that connects to an adaptor bolted to the cylinder head near the top on the drivers side. There is a sensor connected to this adaptor. It is a high pressure hose with bolted connections similar to a brake fluid line. It goes down and back behind the housing that the oil filter is on. It is almost certainly leaking as it is wet. Is this an oil line?

It sounds like you're talking about the Vanos oil supply line. Is it the #15 hose in these pics (may not be the exact same as your car depending on engine)?
I replaced this last week on our X3 since it was leaking on the lower side of the line near the oil filter housing. Make sure to replace the copper washers as well.

The Vanos line was a weep. The leak was the gasket between the oil filter housing and the block. No wonder - the machining on the face of the housing is pitiful - BMW should be ashamed. At the end of the day, it was a fairly simple fix with a few hints from the U tube video showing the repair on a 3 series sedan. And I replaced the belts while there. A good day!