Transmission fluid leak after rebuild

[Denali12]

12 Denali 2WD 6.2L

Aamco rebuilt the transmission, abandoned the original trans cooler, & added an external cooler. They didn’t close off the old lines & sometimes I get trans fluid from them (nothing significant) I also smell coolant if I hammer down on the gas at highway speeds, but all hoses checkout ok. I see the old lines come out of the old cooler or maybe the radiator. Also wondering what the top hose is that runs back to the engine block. This seems to go into the old cooler too? Any thoughts/advice on this?

 

[Fless]

The middle pic of the radiator-to-surge tank is for engine coolant. It's not related to the transmission system. It goes over the intake and next to the MAF, to the surge tank as shown.

 

[Denali12]

The middle pic of the radiator-to-surge tank is for engine coolant. It's not related to the transmission system. It goes over the intake and next to the MAF, to the surge tank as shown.

I had it wrong.. The is the one i'm unsure of. It goes into the same area as the old trans cooler lines.

 

[Geotrash]

I had it wrong.. The is the one i'm unsure of. It goes into the same area as the old trans cooler lines.

That's a steam line that should terminate visibly into a metal line that runs between the cylinder heads along the forward end of the engine valley pan.

What concerns me is their decision to forego the radiator's water-to-oil cooler in the transmission cooling circuit. I understand why they did it - getting it completely flushed of all of the metal particles from the failing transmission isn't always effective, but you need that cooler in the circuit anyway. I know this because I once tried to take mine out of the circuit and add a much larger external cooler. Bad move. I would wager that without that cooler in the circuit, your trans temps are routinely hitting 230+. The right way would have been to replace the radiator, and replace the factory external cooler as well as all of the lines.

 

[Denali12]

That's a steam line that should terminate visibly into a metal line that runs between the cylinder heads along the forward end of the engine valley pan.

What concerns me is their decision to forego the radiator's water-to-oil cooler in the transmission cooling circuit. I understand why they did it - getting it completely flushed of all of the metal particles from the failing transmission isn't always effective, but you need that cooler in the circuit anyway. I know this because I once tried to take mine out of the circuit and add a much larger external cooler. Bad move. I would wager that without that cooler in the circuit, your trans temps are routinely hitting 230+. The right way would have been to replace the radiator, and replace the factory external cooler as well as all of the lines

Thanks for engaging.. I'm learning already.

What was the result when you took it out of the circuit? I've been running like this since December but every time I crawl under to change the oil I notice the trans fluid reside. Either way I'm going to tape off the cut hoses & clean up the trans fluid to make sure the it's not the new hoses/lines that are leaking.

I'd like to fully understand this system. Is there somewhere you can point me to research how the original system functioned? I can't wrap my head around trans fluid & coolant work within the same area. Did the trans cooler lines run through coolant in the radiator? Perhaps the steam line terminating into the same location is why I smell coolant after stressing the engine or maybe I'm actually smelling tranny fluid?

I will start to monitor the trans temp more frequently. What would you say is a realistic ideal operating temp range in the extreme heat of South Florida?

 

[Geotrash]

Thanks for engaging.. I'm learning already.

What was the result when you took it out of the circuit? I've been running like this since December but every time I crawl under to change the oil I notice the trans fluid reside. Either way I'm going to tape off the cut hoses & clean up the trans fluid to make sure the it's not the new hoses/lines that are leaking.

I'd like to fully understand this system. Is there somewhere you can point me to research how the original system functioned? I can't wrap my head around trans fluid & coolant work within the same area. Did the trans cooler lines run through coolant in the radiator? Perhaps the steam line terminating into the same location is why I smell coolant after stressing the engine.

I will start to monitor the trans temp more frequently. What would you say is a realistic ideal operating temp range in the extreme heat of South Florida?

The result was much warmer average and peak transmission fluid temps - you can monitor this on your DIC in the gauge cluster. GM specs the minimum fluid temp for normal operation to be 150ºF and 265ºF max (such as when towing out of Death Valley in the summer). Typical range for the factory cooler setup is 170-200ºF for daily commutes, highway driving and such where you live (ambient + 100ºF, more or less). I tow a 7000 lb camper over mountains often and will occasionally see 235ºF when crossing a pass on a hot day with my current setup, which has more cooling capacity than stock.

The stock transmission cooler setup in the Denali has two parts: an external air-to-oil cooler that sits in front of the radiator, plumbed in series with the water-to-oil cooler in the passenger-side end tank of the radiator. The fluid flows through the radiator end tank cooler and then through the external cooler in front of the radiator before returning to the transmission. The water-to-oil cooler in the radiator is just a sealed aluminum labyrinth chamber that allows the transmission fluid to pass through the end tank and either absorb heat or shed it very effectively. Its purpose is twofold: to warm the transmission fluid faster in very cold weather, and to cool the fluid in very warm weather. It works really well. So well in fact that when you take it out of the circuit, it's much harder to regulate the fluid temperature.

 

[Doubeleive]

Thanks for engaging.. I'm learning already.

What was the result when you took it out of the circuit? I've been running like this since December but every time I crawl under to change the oil I notice the trans fluid reside. Either way I'm going to tape off the cut hoses & clean up the trans fluid to make sure the it's not the new hoses/lines that are leaking.

I'd like to fully understand this system. Is there somewhere you can point me to research how the original system functioned? I can't wrap my head around trans fluid & coolant work within the same area. Did the trans cooler lines run through coolant in the radiator? Perhaps the steam line terminating into the same location is why I smell coolant after stressing the engine or maybe I'm actually smelling tranny fluid?

I will start to monitor the trans temp more frequently. What would you say is a realistic ideal operating temp range in the extreme heat of South Florida?

well the transcooler on the radiator is just a small section inside the plastic end cap it goes in and goes out it does not travel thru or "across" the radiator, the opposing end cap holds the engine oil cooler. you could restore the transcooler function and the added external cooler in parallel you just need a couple lines and connectors to make it happen.
what would bother me is the coolant smell, It's going to be a leak somewhere. take a pen and make a mark on your coolant reservoir while cool and parked on a level surface, make a mark right where the coolant level is and then keep an eye on it. A slow leak can be hard to find but if the coolant drops below the line you made then you know it is leaking somewhere. to find the leak you will need a flashlight & telescoping tilt mirror and get under the truck, you might have to even unbolt the radiator tilt it back and look in front as well.
you will need to look all over primarily on the passenger side, firewall, hoses, reservoir tank,under the water pump, steam lines and even the rear hvac area (rear passenger side)

 

[Geotrash]

well the transcooler on the radiator is just a small section inside the plastic end cap it goes in and goes out it does not travel thru or "across" the radiator, the opposing end cap holds the engine oil cooler. you could restore the transcooler function and the added external cooler in parallel you just need a couple lines and connectors to make it happen.
what would bother me is the coolant smell, It's going to be a leak somewhere. take a pen and make a mark on your coolant reservoir while cool and parked on a level surface, make a mark right where the coolant level is and then keep an eye on it. A slow leak can be hard to find but if the coolant drops below the line you made then you know it is leaking somewhere. to find the leak you will need a flashlight & telescoping tilt mirror and get under the truck, you might have to even unbolt the radiator tilt it back and look in front as well.
you will need to look all over primarily on the passenger side, firewall, hoses, reservoir tank,under the water pump, steam lines and even the rear hvac area (rear passenger side)

Good advice.

And I'll add that if it's happening only under full throttle, you might want to check where the heater hoses go through the firewall. The water pump pressure spikes under full throttle and can stress those plastic tees right there at the firewall, and they're a common failure point. Yours are about due being 10 years old.

 

[Denali12]

well the transcooler on the radiator is just a small section inside the plastic end cap it goes in and goes out it does not travel thru or "across" the radiator, the opposing end cap holds the engine oil cooler. you could restore the transcooler function and the added external cooler in parallel you just need a couple lines and connectors to make it happen.
what would bother me is the coolant smell, It's going to be a leak somewhere. take a pen and make a mark on your coolant reservoir while cool and parked on a level surface, make a mark right where the coolant level is and then keep an eye on it. A slow leak can be hard to find but if the coolant drops below the line you made then you know it is leaking somewhere. to find the leak you will need a flashlight & telescoping tilt mirror and get under the truck, you might have to even unbolt the radiator tilt it back and look in front as well.
you will need to look all over primarily on the passenger side, firewall, hoses, reservoir tank,under the water pump, steam lines and even the rear hvac area (rear passenger side)

Good advice with the pen. I'll do that today. I've been keeping an eye on it & it's actually slightly above the "full" mark. I'm starting to realize the sweet smell may actually be the tranny fluid.

Do you guys think it's normal that those old lines keep spitting fluid?

 

[Denali12]

I crawled under to get a better look & snap a few photos. Found the fluid leak!