It can be the bearing in the pulley.

The tensioner also has a bearing at the base of the swinging-arm where it mounts to the engine's front cover, and that often wears and allows the pulley to ride at an angle.

That's regarding the TD Turbo, T124, not sure what a TDT is (sorry Jimmy) or whether it is a T123, year and proper model will help.

__________________

Gone to the dark side

- Jeff