I’ve had a lot done on my ‘11 G37 xs coupe, way to much to let it go now. Most recent big job resulted in me swapping out my whole transmission due to internally mixing of oil and coolant from the cooler and destroying the initial transmission. I had a new rad put in and flushed twice new thermostat as well. It’s been over a year now and I’m never even putting the car past 4k rpm’s I just want it to drive normally. Upon checking my engine bay routinely I see my coolant tank is pure black. Engine dipstick is clean and head gaskets we’re done after the radiator incident as well from overheating once. Could this be the famous gallery gaskets? I can’t find anyone who had something like this before and suggestions on what it could be before I take it in would be appreciated thanks

 

Did you thoroughly clean the overflow tank when you installed the new radiator? Oil is heavier than water (or antifreeze) and sinks to the bottom of the tank, which is what your pic appears to show. You could also try draining your radiator to see if there is oil mixed with the antifreeze. That could mean a blown headgasket or other serious engine problems.

 

The tank was completely black, the tank was completely clear and clean 2 days prior only thing that’s happened was loss of coolant overtime that I just top up. I’d be very surprised if it’s a head gasket cuz I’ve done then under a year ago. And the radiator cap itself doesn’t have any dirty coolant up top either just the overflow tank