I think I resealed the timing chain cover five times before I got it exactly the way I wanted
The trick seems to be to get all the areas completly clean. I used an old tooth brush and some solvent (do not know the name in english) to clean all areas. I then proceded as describert in the repair manual. As I said it took me five times to get it perfect.
About the oil leak at the oil-to-heat exchanger I have added a picture of the unit.