Thanks, i'll check the airlock.

Oil in water is not always present.

Check for bubbles in radiator/header tank

As for water pump the only sure way is to remove it.  Another method is to
wait till the engine is warm, shut off the car heater controls (set to
cold), and then manually restrict the top/bottom and bypass water hoses.
e.g. clamp the bypass hose fully then manually squeeze the radiator hose.  A
point will come where noise/vibration/flow can be sensed.  How you determine
if this is normal or not I don't know :-)  Of course higher engine revs will
increase flow and 'feeling'.

I'm assuming your Punto has a header tank in which case there will be a
small top return hose.  This should be pushing water into the top of the
header tank.  Depending on the visibility of the plastic you may be able to
see the varying flow with engine revs.  If not you can disconnect this hose,
extend it and poke it into the header tank cap hole and water the discharge
rate.

These are all 'off the cuff' suggestions and may leave you in a bigger
dilema than ever!

Nick /////