I have a small transmission leak that I cannot find the source of! This is final step of a larger project replacing the transmission and radiator/hoses from an internal radiator leak that ruined the transmission. The issue is with the radiator and trans-cooler hoses that from all accounts are leak free.....there is still a small amount of trans fluid that eventually (10-20 minutes after running the engine) finds it way to passenger side subframe bracket then dripping to the ground. See image below. When I trace the fluid back from the drips you see below, the fluid seems to come from the very bottom layer of the brace under the radiator. That metal brace under the radiator is multi-layered with lots of holes on the top layer where the radiator and condenser sit. Logically the fluid would leak from the cooler lines or radiator to the top of the metal brace then drip down through one of the many holes to the bottom layer then out like seen below. But I cannot find any leaks originating the cooler lines or radiator!!!!! Its like the fluid originates somehow between the top and bottom layer of the brace. This makes no sense!!!



I am 99.9% positive there are no leaks from the radiator itself or the trans cooler lines. I have deleted the external trans cooler to reduce connections and lifted the radiator up a few inches and placed white paper towel under the radiator and all connections of the cooling lines with no leaks. The image below shows the radiator lifted up while the engine runs so I could directly observe under the radiator and hoses and no drips!



After running the engine on and off for about 15 minutes there was no dripping.....I put the radiator back in place ran the engine for another 15 minutes. No dripping while I stood there observing. This morning....the drips were back (the first image was taken this morning).

I cannot for the life of me figure out where the trans fluid is originating such that it flows through down the inside of the bracket holding the radiator and out by the passenger subframe bracket. Any ideas?

 

AFAIK all the connections to the trans are in the front. Hard tell color of drip from the image. Are you sure that's not power steering?

 

Hey 619rcr! Yes, the two connections to the radiator are facing the engine (not sure if that is considered front or back). I am 99.9% sure its ATF because its very pink and my PS fluid is tan/brown. I did another experiment. I completely removed the trans line at the bottom of the radiator to rule that out or in. I also removed the two subframe bracket bolts so any ATF dripping through those holes would be more obvious. The image below is after running the engine for two, 15 min segments with no visible dripping.




The two holes I circled in blue are where the subframe bracket bolts were and where some of the ATF trickled down to (the first picture doesn't really show it, but in other trials those bolt heads had drips of ATF) and those are right underneath an ATF connection. Simple logic would say that is the obvious source of a slow leak......but everything I've tested and looked at says no. In addition to just rubbing my finger under the connector and not seeing or feeling ATF, I also put white paper towel underneath but that also did NOT show any leakage. These photos are of the second radiator I installed assuming there was some small leak some where in some place I just couldn't see in the first radiator. This is making no sense. My next step is to connect the ATF lines again, and run the engine again.

Also, the black wire you see clamped to the bracket is my endoscope to see when the fluid accumulates under that top layer of the bracket.

 

I have reconnected the ATF lines and placed white paper towel between each ATF connector and the bracket underneath.



I have also placed white paper towel under that passenger side bumper under where the drips previously occurred. I will run the engine two times for 10-15mins and let it sit and see what drips? Stand by.........

 

Update: Interesting results. after running the vehicle two times for 10-15mins there was a small drip on the white paper towel on the ground and no ATF on the paper towel under the radiator (which is consistent with previous tests). Above the small drip on the ground was another ATF drip hanging on the subframe bracket....but this time the subframe bracket was disconnected from the metal bracket under the radiator (see the below image). It is is hard to see from the image but the subframe bracket was disconnected from the front of the vehicle and swung 90 degs toward the passenger tire. This suggests the ATF is originating further inward towards the engine. In other words, the ATF flowed from an unknown origin making its way to the subframe bracket, then flowed down to the bracket to under the radiator. Which corroborates the lack of evidence of an ATF leak from the radiator or ATF lines. I'm curious what anyone thinks of this theory or another theory. Though it is still very confusing how ATF could get to the front passenger side corner of the subframe. Maybe a large leak at the CV seal that just snaked its way down and forward to the front of the subframe????



I cleaned up the present ATF and trying to reproduce this again to confirm the ATF makes it way to the subframe bracket. Any ideas would be appreciated.

 

Check the transmission oil seal on the passenger side for the CV axle shaft.

If not, recheck all power steering connections and the condition of the pump.

 

Upon closer review, the ATF is not originating from the engine area. With the passenger wheel off i can get a perfect up close view and the geometry wont allow ATF to leak down the subframe towards the front, then "up" to subframe bracket and under the radiator. Plus upon closer inspection the ATF is only seen between the low point of the subframe and under the radiator. My only conclusion is the dripping I saw was simply residual AFT that dripped into the frame from the part swaps and slowly made its way out from driving (vibration and wind). I've deleted the external trans cooler and driving it around to confirm no more drips. If no more drips I will assume my conclusion is correct.

 

Makes sense. I once had a power steering hose leak into the front radiator subframe and it dripped fluid out of every hole in it and the crossmember for a week until I got mad and took the car to a car wash to pressure wash it all (underhood-subframe) with hot soap and rinse it off.

 

Its time to close this thread out. After all the above diagnostics and re-installing the external cooler I have not seen any more ATF drips. My only conclusion is the dripping I saw was simply residual AFT that dripped into the frame from the part swaps and slowly made its way out from driving (vibration and wind). It was an interesting learning experience and completely closes out this large trans/rad project I started in July 2024. Oy! Thanks to all.