Transmission Pan Leaking Coolant

[PerformanceJunkie]

Hey Guys,
I have a 2010 RS V6 Automatic.

I placed die into the coolant and traced my mystery coolant leak to the back of the transmission pan gasket. Its weeping between the transmission housing and the pan. The gasket has failed. I did torque it gently. The bolts were on the loose side...certainly helping the gasket to fail.

It is not leaking and running down the sides or coming from anywhere else.

Does anyone know if the transmission pan gasket has a similar passage like a head gasket that seals a channel of coolant.

There is no coolant in the transmission fluid. I have drained a small amount and hit it with the UV light. Just clean regular smelling trans fluid.

It shifts and runs perfect.

I have built my share of engines. I have never seen this prior.
I searched TSB's couldn't find any on this in a basic internet search.

Thanks for any help in advance.

[40years]

There should not be coolant anywhere near the transmission. Even the cooler lines carry trans fluid, not coolant.

[omgitsmikeyC]

Perhaps its runoff from the head-gasket in the back of the block.... Agreed coolant should not be leaking near there. Better get it looked at or go somewhere you trust. Check oil for coolant also at your next change.

[Scalded Dog]

If there is no coolant in the transmission fluid, I don't see how coolant could be leaking out of the pan, failed gasket or not.

If you are getting dyed coolant around the gasket, I would be more suspect that coolant is leaking from somewhere else, and the aerodynamics of the car in motion tends to direct the coolant directly to that area, giving the appearance of leaking from there. Even if coolant was leaking from elsewhee, and blowing all over the place underneath, it would probably tend to concentrate in a nook, like where the pan meets the trans. I know you said that you don't see it anywhere else but there, but, that's where it WOULD settle in greater concentration (to be visible with the UV light), as opposed to other areas that might be getting coolant that MOSTLY blows off/ evaporates.

Just my opinion, my guess...

[Wizard1183]

Originally Posted by omgitsmikeyC

Perhaps its runoff from the head-gasket in the back of the block.... Agreed coolant should not be leaking near there. Better get it looked at or go somewhere you trust. Check oil for coolant also at your next change.

Wouldnt the dipstick show some sort of coolant on it rather than waiting for an oil change? If he put dye in the system, and it was mixing with the oil, (meaning a busted head gasket) then one would have to think the dipstick would have dye on it?

[PerformanceJunkie]

I'm stumped also....
Oil is clean, trans fluid is clean. Nothing from intake or back of heads. No sweet smell from the exhaust.

Thanks for the suggestions. I'll keep on looking

[Wizard1183]

Originally Posted by PerformanceJunkie

I'm stumped also....
Oil is clean, trans fluid is clean. Nothing from intake or back of heads. No sweet smell from the exhaust.

Thanks for the suggestions. I'll keep on looking

is it strictly coolant you see? If so, its gotta be a hose thats leaking.
Check this out, it might help you to look for that hose thats probably leaking.
its a diagram of your coolant system:
http://www.tonkinonlineparts.com/sho...ssembly=811359

[PerformanceJunkie]

Strictly coolant....no separation of coolant and trans fluid to see at least...would be kind of like oil and vinegar separation with density difference.

Just got done searching again. Only wet spot is between the trans pan and trans housing. Weeping through the gasket. All coolant it appears and glows with the uv light... Had the car up hi and totally under it with a bright flash light. Can see back of the heads and zero leaking down.

Laying on top of the engine feeling back of the heads and every place my fingers can reach absolutely no moisture.

Called Chevy and a tech advised there is a coolant line running through the trans. Need to verify.

Just ran the car for 15 minutes will look again in a while. It after it sits. Nothing running down and streaming / staining a path under the car.

Patience and persistence....

[Wizard1183]

Originally Posted by PerformanceJunkie

Strictly coolant....no separation of coolant and trans fluid to see at least...would be kind of like oil and vinegar separation with density difference.

Just got done searching again. Only wet spot is between the trans pan and trans housing. Weeping through the gasket. All coolant it appears and glows with the uv light... Had the car up hi and totally under it with a bright flash light. Can see back of the heads and zero leaking down.

Laying on top of the engine feeling back of the heads and every place my fingers can reach absolutely no moisture.

Called Chevy and a tech advised there is a coolant line running through the trans. Need to verify.

Just ran the car for 15 minutes will look again in a while. It after it sits. Nothing running down and streaming / staining a path under the car.

Patience and persistence....

yes, it seems there is coolant lines to the transmission. Here's what I found:
http://www.cargurus.com/Cars/Discussion-t42568_ds513593
There is no dipstick/filltube.. Level is checked at the drain/fill plug on the pan..Maint schedule I think says at 50K.. Use Dexron VI transmission fluid only. Failure to use the proper fluid may result in transmission internal damage. From service manual Caution: THE ENGINE MUST BE RUNNING when the trans oil level check plug is removed or excessive fluid loss will occur, resulting in an under-filled condition. An under-filled transmission will cause premature component wear or damage. Note: Continue to monitor the TFT. If the TFT is not within the specified values, reinstall the trans oil level check plug and repeat the previous steps. Remove the trans oil level check plug (1) from the transmission fluid pan. Allow any fluid (2) to drain. If the fluid is flowing as a steady stream, wait until the fluid begins to drip. If no fluid comes out, add fluid until fluid drips out. Refer to Transmission Fluid Fill Procedure (See: Service and Repair). Inspect the fluid color. The fluid should be red or dark brown. If the fluid color is very dark or black and has a burnt odor, inspect the fluid and inside of the bottom pan for excessive metal particles or other debris. A small amount of "friction" material in the bottom pan is a "normal" condition. If large pieces and/or metal particles are noted in the fluid or bottom pan, flush the oil cooler and cooler lines and overhaul the transmission. If there are no signs of transmission internal damage noted, replace the fluid filter assembly, repair the oil cooler, and flush the cooler lines. Fluid that is cloudy or milky or appears to be contaminated with water indicates engine coolant or water contamination. Refer to Engine Coolant/Water in Transmission (See: Symptom Related Diagnostic Procedures\Engine Coolant/Water in Transmission). Caution: Refer to Fastener Caution (See: Service Precautions\Vehicle Damage Warnings\Fastener Caution). Replace the trans oil level check plug and tighten to 25 Nm (18 lb ft) . Inspect for external leaks. Refer to Fluid Leak Diagnosis (See: Component Tests and General Diagnostics\Fluid Leak Diagnosis). Reset the oil life monitor only if the fluid was changed.

[ClawSS]

So this aforementioned TSB would be a break/leak within the tranny cooler & radiator allowing coolant to mix with the ATF in the cooler line flow dumping it back into the pan. That would cause a milky weird tranny fluid.

I got that the OP was saying that the coolant was on the outside of the tranny pan near the gasket area like a coolant line of antifreeze was leaking near the tranny. There isn't one of those carrying antifreeze / coolant.

My vote is overflow blowback or radiator hose leakage blowback accumulating on tranny pan gasket mating surface.

[PerformanceJunkie]

Called the dealer and the GM power train warranty covers seals and gaskets. Not the basics like belts, hoses and crossover pipes, however its a decent warranty.

To the GM doctor it goes. Monday or Tuesday. I'll update the outcome. Thanks for all the help and suggestions.

BTW after reading Lots of info I found a small fix that gave me much more torque and drive-ability.

Simply removing the cam position sensor plugs cleaning the contacts male and female and plugging them back in is a huge difference.

It feels like a different car.

Now I really feel the advantage of the modded throttle body as well.
I had to press the throttle hard enough for the cold air intake to be kind of loud.

Now the same performance with it seriously quieter....far less open on the throttle and it feels great in all the gears. I'm not waiting on the sweet spot of the power band anymore. It feels like its always there. For a 6 banger I cant ask for much more....A lighter car, yes. But the Six is respectable.

[Chevy Fanatic]

Possible the heater core is leaking