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Hello just replaced my transmission cooler lines and at the fitting of the return line it seems to have a small leak. 2008 F250 5.4 3v transmission is auto I believe it’s an 5r110w.
At the return line (the one towards the rear of truck) sticking out of the transmission it has a darker colored fitting that the new line threaded into it has a small leak. I first grabbed a 3/4 wrench and tightened the new line fitting itself and it did get tighter and the leak was less. Now it seems to only have a small leak at the insert at the transmission. I grabbed the 1” wrench and did try and tighten but it barely tightened up any.
the lines were not leaking before repair was done. They where corroded severely towards the front of the truck and quick connects had a split with heavy corrosion under.
My guess is there is some sort of debris on the sealing surface. Continuing to tighten will leave an indentation on the sealing surface that may continue to leak, forever. I would pull the connection apart and do a deep inspection of the sealing surface using a good light, mirror and magnification tool. Inspect both surfaces. Occasionally a new hose fitting will have been damaged in packaging or shipping.
If it were mine, I would consider putting a thin coating of form a gasket, or similar, on the sealing surfaces should you find any damage.
But, that's just me and my environment.
My guess is there is some sort of debris on the sealing surface. Continuing to tighten will leave an indentation on the sealing surface that may continue to leak, forever. I would pull the connection apart and do a deep inspection of the sealing surface using a good light, mirror and magnification tool. Inspect both surfaces. Occasionally a new hose fitting will have been damaged in packaging or shipping.
If it were mine, I would consider putting a thin coating of form a gasket, or similar, on the sealing surfaces should you find any damage.
But, that's just me and my environment.
Hobo
thank you. Yes I’m not going to pull it apart just yet I will clean it down dry then look at it after each long drive to see if it still leaks any. I did put a wrench on it and tighten it but didn’t get much so I’m gonna have to wait and see. But I agree I will have to look at the line where it’s flared and also the fittings and will use some liquid hightemp thread sealant.
in my photos where the arrow is, the larger dark colored fitting that the lines thread into. Do those screw right out? I didn’t want to take the line off just to mess with it because I needed the truck to drive.
thank you. Yes I’m not going to pull it apart just yet I will clean it down dry then look at it after each long drive to see if it still leaks any. I did put a wrench on it and tighten it but didn’t get much so I’m gonna have to wait and see. But I agree I will have to look at the line where it’s flared and also the fittings and will use some liquid hightemp thread sealant.
in my photos where the arrow is, the larger dark colored fitting that the lines thread into. Do those screw right out? I didn’t want to take the line off just to mess with it because I needed the truck to drive.
I'm not sure that hex fitting is removable. I would be hesitant to attempt to remove it since it is not leaking... Let that sleeping dog lie.
I would put a back up wrench on that dark fitting when I remove the new fitting... Just in case.
Update the one line fitting that was leaking is now no longer leaking. I unscrewed the fitting on that one line all the way. Inspected everything and it looked ok. I put it back together the same way as before and it no longer leaks. They are aftermarket Dorman lines so maybe the flare wasn’t perfect or maybe there was some dirt or debris causing the leak. I don’t know but I’m glad it’s all set now and not leaking. Thanks Hobo !
Thank you for being one of those rare individuals who will venture under a vehicle and make their own repairs...
I see hard times coming and the shop rates are still climbing.
The economy / financial world is unsustainable.
Sorry to revive an old thread, but I just recently bought a Dorman transmission cooler line. When I tighten it, it leaves about 3 threads exposed, similar to your pictures. The old one tightens all the way up. The threading is the same, but the flare is slightly thicker. We're you able to get yours tightened down all the way? Thanks!
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