Does he drool all the time? when chester was smaller their was a couple of days he went drooling really bad. He would be asleep and a puddle of drool would be right next to him. From what i was told on this forum and by the vet he could of had something stuck in his teeth. He still drools in the car which is because he's stressed and just doesn't like to ride in the car.
Ben drools when he is really stressed or excited - especially at the dog park. Being near other dogs, even if only smelling them everywhere, gets him started. He won't eat treats and long strings of drool wrap themselves around his face. We don't take him into the fenced area as that is so stressful, but even walking through the park he gets super excited (i.e. peeing 13 times in a 2 mile walk.)
By one year, all major teeth should be set in nnd the drooling due to teething should not be a cause so my first move in case of sudden over-drooling would be to inspect the gums and mouth. The drooling can be caused by something as simple as a sliver of something (wood, rawhide, food) caught between the teeth and the dog trying to dislodge it.