New aftermarket GM radiator leak at trans cooler!

teehee

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#1
Make
Saturn
Model
Outlook
Year
2009
Miles
159000
Engine
3.6LLT
After making it through an engine swap on this vehicle..,I found the radiator had a hole in it during its maiden voyage! I ordered a “heavy duty” aftermarket radiator, proceeded to remove the front fascia (bumper) and swap out old for new. Upon topping off my fluids I found trans fluid dripping, well actually squirting from the lower cooler fitting!!!! It’s in a tight spot and since I already put the fascia back on (big mistake before testing) I opted to remove the fitting from the radiator to have a look. What I found was no O-ring inside the fitting!!!! So I obtained a OEM fitting, complete with O-ring and snap ring, only to find that the threads seemed different, so I just used the O-ring in the aftermarket fitting. Buttoned everything up and all seemed well. After a few days of driving and smelling tranny fluid, I noticed a slight drip, this time from the upper cooler fitting!!!! So here we go again, this time I removed the O-ring, which looked fine and matched it up with a new viton O-ring. Still leaks!!! So I was feeling desperate and not sure what could be the issue, so I went and
got another OEM fitting and replaced the O-ring again....still leaks, not as bad but still leaks! I don’t know what else to do here! Anyone else ran into this before?
 

billr

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#2
If you post some good pictures of the line, fitting, and port in the radiator I may be able to help figure this out.
 
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#4
When I have a problem like this, I will try to pinpoint the leak (tube to fitting, fitting to adapter, adapter to radiator) and then add an o-ring or maybe tape. Finding an o-ring to work requires consideration of what will happen when you tighten the fitting. The o-ring needs to end up being squeezed but not crushed when the fitting is fully tight. A good practice is to tighten fitting, then remove fitting to inspect o-ring for damage. If o-ring looks good, put it back together and check for leaks. If it leaks, you then try a slightly thicker o-ring, and repeat.
 

billr

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#5
Yep, I'm not sure at all what we have here; that's why the pictures will help.

The one problem I have heard of in recent times is that some of the "newer" vendors don't seem to understand that a tap leaves imperfect thread at the bottom of a female port; there has to be an undercut "thread relief" there so the male fitting can go in as deep as OEM. The solution seems to be to grind off the first bit of thread on the male part, providing the needed clearance from that end.
 

teehee

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#6
Well the engineers at GM took all the guesswork and room for error out of this job...nothing to under or over tighten, just a snap ring type of clip holds everything in place. I cleaned everything up real good (again) and drove it for awhile and thought maybe the OEM ring was holding, but it seemed like after running the AC for awhile and bringing the temp up more, it started to drip again!!!! I’m headed to NAPA now to see if there’s a thicker O-ring that will fit. I’m running out of options.
 

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billr

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#7
"So I obtained a OEM fitting, complete with O-ring and snap ring, only to find that the threads seemed different, ..."

Remember that from the beginning of this saga? Now I'm confused; are there any threaded fittings involved or not?
 

teehee

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#8
There are threads involved but that is the connection of the fitting to the radiators internal trans cooler, the leak I have is within this fitting.
 
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#9
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teehee

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#10
Well sometimes it’s best not to overthink this stuff! Following suggestions here for trying a larger thickness O-ring, that may have fixed it. NAPA had some metric nitrile O-rings that were a bit thicker, yet still went together without much extra effort and so far so good. I’ll report back after a few days of driving. I was just about to abandon the radiator cooler and install an external cooler, lol!