Snagger
Explorer
I'd vote for the particle filter too.
For what it's worth, 300Tdis have a reputation for squealing belts and tensioners. For anyone suffering that, the usual advice is to clean the belt and all the pulleys (clean their grooves too). If that doesn't cure it, most will insist it's the tensioner bearing (you can replace just the bearing if you have a local bearing specialist and can get the circlip out) or a misalignment due to the grey plastic bush between the tensioner's mount and arm wearing down. I replaced both with new and still had the same squeal until the engine was warm. The clue was right there - the engine temperature. The squeal is often from the water pump but is frequently misidentified as coming from the adjacent tensioner.
For what it's worth, 300Tdis have a reputation for squealing belts and tensioners. For anyone suffering that, the usual advice is to clean the belt and all the pulleys (clean their grooves too). If that doesn't cure it, most will insist it's the tensioner bearing (you can replace just the bearing if you have a local bearing specialist and can get the circlip out) or a misalignment due to the grey plastic bush between the tensioner's mount and arm wearing down. I replaced both with new and still had the same squeal until the engine was warm. The clue was right there - the engine temperature. The squeal is often from the water pump but is frequently misidentified as coming from the adjacent tensioner.