My neighbor has a 2008 535i twin turbo. It has suddenly developed a big oil leak. He asked me to look at it and I identified the oil filter housing to be leaking. We fixed that but the big oil leak is still there. It seems to be all over the bottom of the car, as well as the turbo area, and a couple of hoses at the front of the engine.

There can not be that many places for a oil leak that big. A 20 inch puddle on the driveway over night.

What are we looking for? The turbo oil lines?

 

Usually it's the oil filter housing however with that much oil did you check for damage to the lines to the oil cooler? Best bet is to wipe down everything and check every hour to trace where the oil is coming from. Did you make sure that all the gaskets were seated and bolts were all torqued down correctly?

 

How about the two small o rings on the oil lines that connect to the underside. You would have had to remove these to change the housing gasket. Did you replace the O rings?

 

The 4 o rings are all fine. They are not leaking. THe oil cooler is not leaking. Something else like turbo oil line I think.

 

Well the only real way to find out is take the underbody panel and cross brace off to inspect the oil lines to the turbos. Also was the car driving fine prior to this issue?

 

When my oil filter housing gasket on my 2009 535i was leaking, it made a mess so bad oil was dripping on the floor in the garage, and oil had run down various hoses to the turbos, getting them covered in oil as well. at first sight I couldn't tell what was leaking, and thought the turbo center sections might be spewing oil.

It was actually just the filter housing gasket - just a big mess - so I would replace that, clean everything up, then keep an eye on it.