Any idea where this leaking is coming from besides from the left side? Any swelling in the cheek area? Does it get worse during mealtime?
I'm guessing it may be an infected parotid salivary gland? That may explain why its leaking only on one side as its only one infected gland. If there's pus buildup in there, instead of having saliva made, it makes pus instead.
I think we need your more descriptive query to come up with an adequate answer. As Jerome said, is leaking area other than left side. Get consultation of your dentist on parotid gland. Is the gland get infected?
the leaking seems to come from the upper part on the tongue side of my tooth. and around the lower molar #18. It does seem to increase after eating. But then again, I brush, floss, and mouth wash before bed and about 30mins later(after laying down) the horrible taste is back. My long time dentist didnt have an idea what was going on. And sadly did not seem at all interested in investigating it future. I am hoping the next (new) dentist, who is a section head of dentistry at a major hospital, will help. I will mention the gland and see his thoughts.