What symptoms would I be looking at if exhaust gases were mixing with the coolant? I have lost some coolant over a long-ish drive and cant seem to put my finger on an external leak. The car hasnt overheated, I monitor both oil and coolant temps. The oil filler cap looks like this after a short drive, coolant up to temp oil not. (could be condensation): I havent checked the dipstick yet but will after work. Through the bottle the coolant appears to have an orange/brown layer on top, again I havent checked as only just turned the engine off. I know the best thing to do is take it to a g