Audi A3 1999 1.9tdi deep constant groaning noise whilst drive, happens without braking, starts deeper and gets quieter with more speed.

In addition, glow plug light comes on Intermittently which I don't think is related.

Local garages seem to be useless so I would like to check issues myself with help from anyone on here. Ordered a diagnostic kit for the Glow plug issue but the grinding seems more mechanical and hasn't shown by way of a light on the dash. Please help anyone!!!!