Cylinder head leak upper cylinder head bolt

Russel: This doesn't necessarily mean a corroded head stud. 

When the bolts are fitted you use a sealant on them. This with age could have given up. As a first step you could try removing the head bolt (must degrease before refitting) and refit with new sealent (drain coolant before procedure).

This is a chance attempt that may well work and buy you time with your engine -worth a try! If this fails then you need to remove the head on that side for inspection before a conclusion on the work to be carried out.

DO NOT JUST TRY TO TIGHTEN IT! This will not work and will just put more strain on the stud.