i have an ideal isar he35 and like the op it has a small leak where the
return pipe enters the heat engine, it is also held in place by a plate
secured by a small bolt/screw, the leak appears to be coming from one
of the sump screws adjacent to the return pipe although the water may
just be tracking to this screw. in your experience would the heat
engine have failed?, its only 14 months old, or is it more likely to be
a loose screw/ bad connectioin? i was tempted to try a proprietry brand
of leak stopper, would this work, are there any problems associated
with using leak stoppers?. i did phone ideal and explained that the
boiler was just out of warranty and that the leak appeared to be quite
old, however they 'only have enough engineers to cover warranty work',
but if i have it repaired and send them evidence of a long standing
fault they will consider bearing the cost

thanks