I am new-ish owner or golf mk4 1.9 tdi and there is a strange sound coming from left side of the engine. Anyone has idea what could make that sounds? Sometimes its there, sometimes i don't hear it and sometimes it goes from high pitched to lower pitched. Its mainly happening from idling to 2.5k rpm. I have made a video, in which can be heard that it goes away after a few secs but it will come back at random times. Its happening when the engine is cold and also when its warm. Anyone has idea what could make those sounds?
Video:
Video: