Hi Rosenicola. There was a recent (ish!) posting about the way that dogs "savour" smells, by chattering their teeth. Is this a par tof his, erm, "repertoire"?
Does he get plenty fresh water when out on walkies?
I am sure other ABers can give much better answers! If it's a real concern, try and get him into the vets sooner.
Yes, he always has access to fresh water, especially with it being hot recently.
I'm not too worried as he is always fine afterwards. I forgot to mention that he slavers too whilst foaming. Sounds horrible i know, but i just thought someone might know as i was a little worried.
how long have you owned him? have you rescued him? if so do you know his back ground? he might be scared of something/ it might be a stress thing or as leelapops said it could be that something smell too good! maybe a bitch in season in you area?
how long has he done this?
If he has done it a few times and shows no other symptoms of ill health, I don't feel it's much to worry about. However, if it does cause a niggle, it'll be �20 well-spent to get him to the vet :)
Give him a big hug from me (I have a BC so I am a bit partial!)