[535_BiTurbo]

Today I noticed my coolant was milkshake colored. I just replaced my waterpump/thermostat last month. So for the past few weeks ive been monitoring my coolant levels. On Thursday my coolant was normal, i drove the car probably 5-10miles total and on Friday i checked the reservoir and its milkshake colored. No engine overheating issues, no burning smells, no transmission issues or codes, etc. I checked the engine oil and its normal colored, so no coolant in engine oil. I pulled the radiator drain plug and coolant is normal color. So then I pull the transmission oil plug and milkshake colored oil comes out thats the same color in the reservoir.

Could the trans cooler in the radiator be leaking or is the transmission heat exchanger leaking??

[Surly73]

Just a heads up the transmission fluid is green - not sure if that could be a red herring.

How's your OFHG?

[n3985]

Short trips won't let the car heat up enough which will result in milky goo around coolant caps. Take a 50 mile drive and check again to easily rule this out.

[535_BiTurbo]

car is a 2012 550i 2wd with the 8hp70 tranny.

[chipguy]

Seems like the coolant/transmission fluid heat exchanger. #9 in the picture

[Surly73]

Originally Posted by n3985

Short trips won't let the car heat up enough which will result in milky goo around coolant caps. Take a 50 mile drive and check again to easily rule this out.

That's true of oil caps due to condensation forming in the crankcase and on the inside of the valve cover and then being emulsified like mayo by the engine running. This is not true of coolant.

[535_BiTurbo]

should i replace heat exchanger, drain and refill the trans or flush, replace pan & filter and heat exchanger and refill?

[Surly73]

Originally Posted by 535_BiTurbo

should i replace heat exchanger, drain and refill the trans or flush, replace pan & filter and heat exchanger and refill?

I asked you about your OFHG condition, and whether the job has been done. If the gaskets in that sandwich are toast, you could be mixing fluids.

[chipguy]

I would try to change as much of the transmission fluid as possible by pushing the fluid through the torque converter etc. Some people might call this a flush. It is important to use the correct fluid ZF lifeguard 8. Also you have to flush the coolant.

[535_BiTurbo]

Originally Posted by Surly73

I asked you about your OFHG condition, and whether the job has been done. If the gaskets in that sandwich are toast, you could be mixing fluids.

OMG dude its not a OFHG, I have a N63 (2012 550i), also my transfluid is not green. When new its clear colored.

[535_BiTurbo]

Originally Posted by chipguy

I would try to change as much of the transmission fluid as possible by pushing the fluid through the torque converter etc. Some people might call this a flush. It is important to use the correct fluid ZF lifeguard 8. Also you have to flush the coolant.

Thank you!

[beegeezy]

FWIW, the image that Chipguy posted is for a N55. You want #1 (17217638580) in this diagram:

and also Surly73 is correct, the ZF Lifeguard 8 is green:

https://www.europaparts.com/zf-lifeg...d-1-liter.html

And to your original question, I would try to pressure test your cooling system to find where it's leaking/mixing with the trans fluid.

[535_BiTurbo]

Originally Posted by beegeezy

FWIW, the image that Chipguy posted is for a N55. You want #1 (17217638580) in this diagram:

and also Surly73 is correct, the ZF Lifeguard 8 is green:

https://www.europaparts.com/zf-lifeg...d-1-liter.html

And to your original question, I would try to pressure test your cooling system to find where it's leaking/mixing with the trans fluid.

Its either leaking/mixing at the Transcooler Heat exchanger or the radiator. Im just going to replace both. They both have 175k miles on them and I have to drain the coolant and remove the electric fan to get to the transcooler.

[chipguy]

You might want to consider changing the thermostat while you are at it.

[535_BiTurbo]

Originally Posted by chipguy

You might want to consider changing the thermostat while you are at it.

where is the thermostat?

[chipguy]

Front of the engine.

[535_BiTurbo]

Originally Posted by chipguy

Front of the engine.

Ive already did this when I replaced the waterpump 2 months ago

[535_BiTurbo]

jar on the left is the fluid that came out of my transmission. The jar on the right I added water to it and Not pictured is a 3rd jar i did, where I added coolant/water mix, and that mix was at the bottom and trans fluid was at the top