HP Officejet 6300 All-in-one machine makes black streaks

The problem is that that there a small piece of glass that the doc feeder use's to scan the orginal. You will have to clean the small glass it's about a half of a inch piece and is normally under the doc feeder unit. It will either be to the right side of the main copy board glass or it is under the doc feed unit where the paper goes down through the feeder. It is mostly some white out on the glass, just clean with a dam cloth with water or windex..... Good Luck