GVee

my coolant looks pretty dark and dirty. I replaced it last year with the red G12 fluid last year. I'm thinking that it might be a leak in the oil cooler or that tranny fluid is mixing with the coolant.

How can you tell if its motor oil or tranny fluid thats in the coolant?

Also is it easy to replace the oil cooler?

Does someone have a write up or instructions on how its done?

CK:1.8T+Rabbitâ„¢

Especially if you were using G11 (Green or blue) before. G11 and G12 are not compatible. What year is the car?

GVee

I did a comlete flush of the system when I refilled with G12 last year. Its only recently that the coolant has been looking dark.

'92 audi 100S

CK:1.8T+Rabbitâ„¢

Yep, check for leaks. Particularly down by the oil cooler.

Brdman*

Flush the system again, maybe its just cleaning the engine out?