2004 Yaris 1.4 D4D Engine Sounds Like Bag Of Nails

[JDBARNES]

My mum has a 2004 Toyota yaris 1.4l with the diesel D4D engine in it. It has been running completely fine the last few months however, recently, after driving around for a bit, the engine sounds horrible. Literally like a bag of nails however, as soon as you stop and turn the engine off then back on again, it sounds completely fine again. This seems to only happen after driving around for a little while. It sounds like it's coming from by where the alternator is/timing belt so im not sure if a bearing has gone or what. The alternator is charging the Battery fine and the car starts up perfectly. I will be servicing it soon to see if that makes a difference but if someone with alot of knowledge on these engines to give me an idea on what it could be, thanks 

[Madasafish]

How many miles?

When (miles and date ) was it last serviced?

Have you checked the oil level?

 

Using the correct grade oil?

Toyota oil filter..

Sounds to me like oil starvation of the engine top end...  If you have the wrong grade oir a filter clogged when the oil warms up.. it could be  low oil pressure.

 

But really I have no clue...

[JDBARNES]

Cheers, i will hopefully be servicing it this weekend so i'll keep everything in mind. It is fairly high mileage (about 124,000) but it has been pretty well looked after by previous owner judging by the logbook.