Trans cooler lines leak at radiator

[200kss]

I've installed 2 new radiators in 2 different cars. 1 a higher end aftermarket aluminum radiator and the other a standard plastic/aluminum replacement. Neither of them will seal at the upper transmission cooler line port. Adding Teflon tape to the threads slow the leak down to just a trickle

 

[-83MONTESS-]

Are you using the right fitting? Is it a pipe thread or straight thread?

 

[pontiacgp]

if two rads leak and teflon tape only slows it down I would be looking at the flare on the pipe, you'll probably have to cut it off and flare it again. The tube nut is probably ok to use it again

 

[565bbchevy]

What are your trans lines made of?

 

[200kss]

These are original lines, that did not leak with the previous radiators. Hard to believe both new radiators have issues but I have verified the lines are not cracked nor cross threaded.

 

[565bbchevy]

2 radiators with the same issue make the lines most likely the culprit, You can replace the lines with Cunifer tubing and they will seal better.