You've still have not said if its 16 valve, SO I'M LEFT GUESSING ..if so, the injectors pass through the rocker cover ..and leaking injector washers can pressurise crankcase and within .
The engine with such is called the 1.6 HDI TDCI as far as i can find out
Here's an ebay listing with pictures of the combined rocker cover / camshaft carrier(if i'm right) showing the injector holes and i think glow plug holes ..all will be buried beneath other plastic covers.
https://www.ebay.co.uk/itm/127055395892?
Don't know much about this engine ..ive been here about 4 years and we've only had one thread with someone owning one, and that was a couple of weeks ago. and that was the 1.5 version ..different again, (well when compared to those pics on ebay.)
They are more commonly fitted to the other ford cars like the focus as well as Citroen and Peugeot.
all the best.mark