300tdi radiator oil cooler change

Hi Chaps,
Done a search but cant find what im after.
I have a 94 disco 300tdi and may rad is roten, Ive bought a new one and new oil cooler pipes, My problem is the oil cooler on side of rad is this always full of oil or does it drain back to the sump?, If it is full of oil do i top up and bleed new cooler once fitted or will it do it itself, And i just need to check engine dipstick level and top that up .
Thank you in advance for any help. Clive.

Dont worry about the cooler it will be fine just top up the oil if it needs it.

Hi and thanks for the reply,
So does that mean it drains back into the sump then, Cos i was worried that if it was held there with a thermastat only opening when hot, I may have to bleed or top up.
Thanks Clive.

You may have to top up but you dont have to bleed it.
There will be some in the cooler but not a great deal.

Thanks a lot for the help. Clive.

Useful to know as I might have to replace my rad soon.

[managed to pinhole it when I was replacing the PAS pump]