FD3s Type R1 oil coolers

[Carrington]

Hi all, My drivers side oil cooler got punctured so brought a second hand one to replace it. For some reason the oil pipe unions will not screw in the new cooler. Does any body know if there are different thread sizes for different years and models of FD3s? All the brackets are the same as the one I am replacing so is definitely the correct one.
 
Thanks