Why does coffee come out while pouring in water its a bunn 10 cup coffee maker
The Bunn has a little stopper that closes the water drain port in the reservoir while the lid is open. You can see a little white plastic pin protruding up out of the grate with the lid open. When you close the lid, it pushes on that pin which causes the stopper to lift off the drain port, allowing the water in the reservoir to enter the heating tank.
If water is entering the coffee basket BEFORE the lid is closed, then something is wrong with that little stopper. It may have a chunk of debris on it preventing it from sealing, or it may be deteriorated, torn, disconnected, etc.
Only way to know is to remove the the screws in the grate and pull the top off exposing the reservoir, and the stopper assembly. The little plastic flapper disc should be seated in the reservoir drain port. It should be relatively flat (not wrinkled) and covering the drain port completely. Test it by pouring some water into the reservoir. If it drains out without you activating the stopper, then a repair is needed.
Move the lever up and down and check its operation. The arm must move freely and close when released. There should be no dirt or debris on the sealing surface of the flapper nor on the sealing surface of the drain port. Gently clean with vinegar as necessary. If the seal is damaged, then a replacement is required.