So last winter it got way colder that I thought it would in the deep south. As a result I blew out my thermostat gasket and my heater core. Repaired all of that and now I've got coolant in the trans fluid and vice versa. My radiator was new about a year ago. I hope it is only that, but I'm seeking advice from you gurus to describe other possibilities. Maybe seals or gaskets in the lines?

Any advice would be greatly appreciated. Except the advice to keep a proper level of anti-freeze in the system. Duh, I done already node dat.

 

The only place where coolant and trans fluid would share a location is in the radiator, it doesn't matter how new it is, if there was no coolant in the water and the water expanded when it froze I am sure it cracked the radiator and that is why you are getting mixed coolant/Trans Fluid, so replace the radiator and hope nothing else bad happened.

 

You should ALWAYS have the recommended coolant / antifreeze in your system as it is needed to protect the aluminum engine, radiator etc from corrosion.

Also you'll need to completely flush the transmission fluid (that entails more than just dropping the pan - you need to find someone with a transmission flush machine) or you will next be looking at replacing your transmission . . .

 

I am sorry to hear this happened. With my time writing service at Mercedes, this was a very common occurrence on the W203 C-Class. Unfortunately, only about 30% of the cases were solved with a new radiator and flushed transmission. Once the frictions in the trans absorb the coolant, it is almost always game over for the trans. With that said... as stated above, replace the radiator, drop the pan and the valve body, drain the converter and flush the system by tapping into the cooler lines.

 

Thanks for the replies. I've got a new radiator and trans filter kit on order. I don't think this was going on very long, because once the ATF hit the cooling system, the resulting foam caused the car to overheat. I was only about 2 blocks from home. Wouldn't the ATF pressure be greater than the coolant pressure? I'm hoping the ATF was present in the cooling system longer that vice versa. We'll see. It was a stupid rookie mistake from someone who's been around a long time and knows much better. Just got sloppy and lazy.

 

Yes until you shut the car off. Then pressure in the radiator would be greater.

 

"Yes until you shut the car off. Then pressure in the radiator would be greater."

That was what I was hoping. Perhaps when the car overheated, that was the first breach and as I said earlier, I was very close to home and haven't driven it since. So maybe everything is not totally FUBAR.

Please, if I am delusional, don't burst my bubble quite yet.

 

If there is even a POSSIBILITY that antifreeze got into the tranny, do not let it sit any longer. Flush that sucker out NOW!