Td5 problem elimination question

[Chanoo]

Hi, I have a 2002 defender td5 and I've had the issue of diesel in the coolant for a while. Is it correct that this issue will come from one of two places
1. The fuel cooler is stuffed
Or 2. There is issues with the head.
So in order to try and find out if the fuel cooler is the issue what I did was- after
several flushes of the cooling system to ensure as clean water as possible I disconnected the fuel line from the fuel cooler and joined them together, thus the fuel system no long passes through the fuel cooler (a temporary measure).
I did this thinking that of the cooler is the issue I would no longer have diesel in the coolant.
Is my thinking correct that no fuel lines
Into the cooler and I'm still getting diesel in the system means that the issue is somewhere other than the cooler.
If so what and exactly is the problem, is it the head and or fuel rail? ☹️
Thanks

[Tombie]

The fuel rail is cast into the head.

So it’s likely cracked if you’ve bypassed the cooler and still having the issue.

Are you sure it Diesel and not Oil?

[djam1]

If you confirm that it is diesel and not oil put an AMC head on it problem solved.

[Chanoo]

Hi tombie,
I replaced the oil cooler the other week, after I got this out of the coolant tank 1st image.
The second and third images are what I got today from the overflow tank and the top radiator hose when I disconnected it
What do you think?