When I fill my expansion tank to the top, I see a steady stream of bubbles coming out of the little hose that goes across the radiator. However, I don't seem to be using any coolant (only driven the car 800 or so miles), don't have coolant in the oil, or oil in the coolant. When cold, pressure doesn't build up in the cooling system unusually fast. The radiator cap is good and after a hard run the hoses are rock hard. After a recent VERY hard run (multiple 0-100 runs), a pint or so of coolant leaked out... which is when I found the bubbles.
I think it is likely a cracked head.... IIRC, one of the (many) reasons a #14 head would fail is high exhaust back pressure from a clogged trap ox. Well, there wasn't a trap on this car when I got it, but the cat. was so clogged up the only exhaust flow was through the EGR valve (that was interesting to diagnose!).
Here are two videos of the bubbles....
http://www.youtube.com/watch?v=kYcg8uUoG5I
http://www.youtube.com/watch?v=pARyVwRha6Q
Thoughts anyone?
Edit: Sorry... this is for my '87 300TD