I know that this is a pain, but you may start by checking all your bolts
and nuts for tightness. Engine cold, go for the 2 temp  sensors, the 3 nuts
that hold the pump to the block.Dnt remember if you can reach it , but the
2 bolts thathold the thermistat housing to the pump(It is a 1.9,
right?).Got a/c? So sorry. The little hose that is under it is a suspect.As
a last resort before major  mechanics,maybe use a radiater stop leak. Wont
work for head gaskets or hose leaks,but for a stiff steal ar aluminum leak
at a gasket , it will work. this may tellyou if it isa hose or not.