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Coolant And Trans Fluid Mixing?


jsp00n

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I got the oil changed in my wife's 02 Yukon Denali and noticed that the truck was leaking from the front passenger side wheel well. I took the truck back to the shop and they told me that somehow my transmission fluid and coolant were mixing and filling the overflow tank to the point that the overflow was pouring out a nasty milky mixture. Any ideas how this is happening and the best way to fix the problem?

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I got the oil changed in my wife's 02 Yukon Denali and noticed that the truck was leaking from the front passenger side wheel well. I took the truck back to the shop and they told me that somehow my transmission fluid and coolant were mixing and filling the overflow tank to the point that the overflow was pouring out a nasty milky mixture. Any ideas how this is happening and the best way to fix the problem?

 

The only place the two could meet is in the radiator....

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So, I should replace the radiator to fix this problem?

If you are sure it is trans fluid, then the cooler in the radiator has sprung a leak. Only way to fix that is replace the radiator... BUT... how can you be sure that the mixture isn't engine oil and coolant (this is the much more likely problem) I'd sure get it checked before you end up losing an engine or transmission due to contaminated lubrication. Not fun!

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well when they did the oil change, they topped off all my fluids and today the dipstick for the transmission was dry. I checked the oil and it seems fine. Thanks for the help.

 

Once the radiator is replaced I'd flush the cooling system as well....

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I got a similar problem> I took my 07 sierra to a dealer to check on a stabiltrac problem. Here is the diagnosis I got from them> keep in mind i have 70k miles

 

no transmission fluid on dipstick

transmission fluid all in radiator

suggest replace radiator and hoses.

 

The quote I got was off the charts $1900. But I wanted it covered in warranty because the transmission failed (it had no fluid). The dealership said they had to replace the radiator first before they could determine a problem with the transmission. I took the truck to a local "reputable" mechanic and replaced the radiator and hoses $700. But I still have the problems shifting gears. So I have to take it back to the dealer to determine what I already knew in the first place (the trans is shot).

 

Heres my question> Can the "transmission problem" cause problems with the radiator. I.E> could the problem with my transmission now lead to a new problem with my new radiator???

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It sounds like a trans cooler leak. The distinction is easy to make, oil contaminated coolant will be greyish brown foam, trans contamination turns into a pink foam that looks a bit like a strawberry milkshake. Have the radiator replaced or atleast the internal cooler replaced, thats the only place contamination can take place. Have the cooling system THOROUGHLY flushed. The biggest problem with these leaks is not trans fluid in the coolant it's coolant in the trans. Even if your trans is empty usually at some point coolant will leak into the trans and then you have problems. The following is straight from the general on what to do if there is coolant contamination in the trans.

 

Important: If water or coolant is found in the transmission, the following steps must be performed:

 

Remove the transmission. Refer to the appropriate SI procedure.

Disassemble and inspect the transmission. Refer to Unit Repair Automatic Transmission - 4L60-E/4L65-E or 4L70-E.

Important: If water or coolant is found in the transmission, the following components MUST be replaced.

 

• Replace all of the rubber type seals.

 

• Replace all of the composition-faced clutch plate assemblies including the band.

 

• Replace all of the nylon parts.

 

• Replace the torque converter.

 

• Thoroughly clean and rebuild the transmission, using new gaskets and oil filter.

 

• Flush and flow check the transmission oil cooler using J 45096. Refer to Corporate Bulletin Number 02-07-30-052D or newer - Automatic Transmission Oil Cooler Flush and Flow Test Essential Tool J 45096 TransFlow .

 

I'm not the trans tech here so I have never gone this or the cheap route. I have seen some guys try the cheap route which is to replace the radiator and perform alot of flushes on both systems, replacing the trans filter every couple of flushes. That is a crap shoot at best (or so I hear) and is never a guarantee that the coolant in the trans will not cause problems down the line. I have seen the internals of one of these transmissions after multiple flushes and there was alot more coolant left over in the trans than you think, you can't ever get it out of the torque converter and coolant will swell the seals and clutches in a short amout of time.

 

Good luck to you, either way you go it is very labor intensive if any coolant did make it's way into your trans.

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Just adding a bigger cooler will not fix the hole in the internal trans cooler in the radiator, possibly causing coolant to get into the transmission, requiring the costly overhaul mentioned above

 

 

If he bypasses the internal trans cooler located inside the radiator and blocks off the inlet and outlet, the coolant cannot get into the trans or anywhere else because the lines will be disconnected.

 

This could certainly be done and save him from replacing the radiator. However, he will need a large (11 x 11 x 3/4) stacked plate cooler at minimum to keep the fluid temps down. This would double the size of the OE external cooler.

 

I would suggest he try this, flush the cooling system at least twice with a HD flush and not one of the 10 min quick flushes. Be sure to run the heater both front and rear on high during the entire flush as you will have trans fluid in both heater cores.

 

He has already received some good info on the trans. I believe I would have to try to flush it out if at all possible and see what happens in the coming weeks

 

Good luck to you and we would love to know what you end up doing.

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