Pressure testing tranny cooler

So after checking my tranny fluid I noticed it was pink and strawberry milkshake looking... I decided to pump it out and refill with dexron III and run for a few hours.... Still pink so I pumped it out and ran again for a few hours... The color now looks like this.

Not sure if it should be changed again or ran longer... I decided to pull my oil cooler to test it as that could be the only source of water in my tranny(bilge stays dry). I plugged one side of the cooler and hooked the other side up directly to a hose pipe and turned the water on full blast.... I left it like this for 10-15 mins and I noticed no water coming out of the oil sides.... Does this mean my cooler is okay?

It's hard to see in that picture but it's still watery

I just replaced my heat exchanger on my engine. I was losing about a gallon of antifreeze a day. It wouldn't leak when it was running, only when it was sitting. I don't know why, but any pressure on the system seemed to seal it up. Try turning off the hose and let it sit over night. It might leak then. Also, if you have access to an air compressor, you could try and test it that way. I'd definitely turn the pressure way down though.

You could always take it to a local radiator shop too. I had mine tested for the price of a couple sodas.

Do you know what kind of water pressure you have? I have seen water pressure as low as 30 psi in my town, mine is actually 90-95 psi. I'd probably change oil one more time & see if it continues to clean up.