Originally Posted by Gibson
There was oil on the rear right side of the base of the cylinder head that concerned me. With the head gasket failure and possibly of cracks I've heard of on the 300tdi's. Looks like it's a bad O ring on a return line. Looks like a emissions system hose?
The thing you're pointing to in the picture is called the cyclone filter.
There is a small o-ring where it goes in to the valve area.
This o-ring is designed to fail and leak every 6 months.