It is not normal for a 16 month old to drool. Let the child be examined by a paediatrician for proper diagnosis

Drooling in children normally resolves with time. Sometimes it can be a sign that baby want to erupt new tooth. In an otherwise healthy baby, there is nothing to worry about.... Some babies drool saliva as habit which they outgrow. However if there are other medical issues for example delayed developmental milestones... Kindly see a Paediatrician preferably a Paediatric Neurologist for further evaluation