Please advise:
I am now assembling my '83 1.6D engine but have a snag.
There is a heat exchanger between the oil filter mount and the filter.

Q: What exactly does this exchanger do?

This metal box has two hoses going in and out and is held on by a large
threaded tube which the filter screws into at the lower end.

Q: Which is the pressure end, this tube or the outside?

The gasket set I have which is very complete does not have a sealer for the
top of the exchanger and I don't remember how it looked when I took it
apart.

Q: Is this exchanger even standard equipment?

It seems like there should be some copper rings or something for the metal
contacting parts but no such sizes are found. Does anyone have an exploded
picture of this assembly that can explain to me what to do?

Thank you for any help here.

                            Rachel