Yup, that's coolant alright. Sorry but it's time to replace it. It would be nice if it could just be repaired but nobody has been successful doing so.

Now for the why, why, why question... Why do you guys run regular coolant in your cars? I have yet to see someone have this issue with the MB coolant whether it is the factory blue stuff or the replacement amberish-clear stuff. I know you're all probably wondering why it matters but the fact is that the green coolant does not have the anti-corrosion properties that MB coolant has. Everyone is careful to not use conventional oil in their motors but when it comes to coolant, they never think twice about using the green stuff.

Since you have to replace the IC, I'd recommend flushing out your system completely and then switching back to the recommended MB coolant before you swap it out. No reason to run the old crap through the new one and you're gonna have to drop the coolant anyways.

Good luck