After making a mess of my not very old radiator by cross threading (an also not very old) oil cooler pipe, ive bit the bullet and bought a new rad.
what I can't seem to work out is the best way to fit the cooler pipe to avoid oil leaks, but also not wreck the rubber o-ring.
It makes most sense to me to fit the o-ring to the rad first after greasing it up, then push the cooler pipe in to it.
But I tried that numerous times before I bust the thread and each time it would take a LOT of force before breaking the o-ring.
Trying it the other way, fitting the o-ring to the pipe first it compresses when screwing the union down and results in oil leaking.

I must be over complicating things here, but had a similar issue when doing the heater matrix - and ended up making a mess of that!!

How does everyone else fit oil cooler pipes? Im even thinking of putting them on the new rad first before installing it.

Any advice before I have a go at this in the morning much appreciated. .

somethings not right then you fit o ring to pipe then fit pipe all the way in then tighten nut ,are your o rings poor or wrong size

When I did mine (same radiator as what you have got) O rings fitting in the nut, then just tightened onto the cooler pipes.

I agree with previous post fit the o ring to the pipe, such that it is compressed between the flange on the pipe and the rad. The o ring should not touch the nut.

The pipe should fit easily into the rad even with the o ring fitted, if it doesnt I would say the o ring is too "fat"?

Cheers folks maybe the bag of o-rings I got previously were wrong.
Ive bought a new cooler pipe which has come with an o-ring so hopefully all will be ok

The replacement went in easily, im pretty sure I have been over tightening those unions in the past mind!