(2014) ISX15 coolant help!

[Nilao]

Well, the prostar coolant bottle is designed so the return line from the thermostat housing sprays into the top of the reservoir so it's possible that is what you're seeing. As far as the combustion gas test I wouldn't do it unless you are pushing coolant out of the cap. The coolant having black specks in it...I guess it could be dirt. I'd run it and watch it like a hawk.