New radiator trans cooler lines leaking

Not sure how aggressive I can get with tightening these fittings up.
I have swapped hundreds of radiators, and I don't recall having this much trouble. It seeps a little, around the threads.
This will be the third radiator that has been in the car over its life, do flares eventually wear out?

You can re-flare or check the thickness of the flare on the end of the tube, but usually they don't "go bad" unless they've been way overtightened on a steel mating fitting.

I've had some of the female fittings not be tapped all the way which results in a slow leak like you describe since the nut gets tight, but it's not squeezing the tube tight to the mating part in the radiator.

You can take a file or dremel tool and cut off 90-180 degrees of the first thread on the nut which will allow the nut to turn a bit farther and seal things up.

Well, I fixed it. I unscrewed both to check for burrs or debris, and seeing none, I (carefully) gave 'em hell.
I do know my own strength, it has been said that I am the type of person that can dent cast iron with a rubber mallet, so I suppose I was just being a little too careful.

Glad you got it to stop leaking!

Might be good to give it a check/re-tighten after a few thermal cycles.

What happened to the other 2 radiators?

Fix Until Broke wrote:

Glad you got it to stop leaking!

Might be good to give it a check/re-tighten after a few thermal cycles.

What happened to the other 2 radiators?

the last rad lasted 9 years, then the tank split. The one before that, was before my time of ownership, so its a mystery. Although the car was in a front end collision at some point so I can extrapolate a failure there.