This is a generic image, but all of my 120/estelle radiators have this 8mm inlet pipe on them and I could never figure out what are they used for, so I just epoxied them off. On my original radiator there was a screw put on it to block it off.

I had this sneaking suspicion that the bleed hose would've connected there, but that can't be right.

 

Anyone smarter than me want to shed some light on to this mystery pipe?

Okay I now feel a bit embarrassed, the bleed hose DOES connect to the radiator inlet.

I went and bought a second Škoda 120 in factory condition to see where it connects.