Unusual overheat

I have a 94 honda civic ex with 1.6 vtec and the car has 162,000 miles. Vehicle at cold start all the way to warm up and even if you let sit there running for an hour will not overheat, while driving vehicle it still wont overheat. It only happens after a long drive when you come to a stop it will overheat but if you start driving it will be fine. So it only happens at idle after driving. After further inspecting it appears to have a little bit of oil in coolant not much though. Also coolant level always seems to low not extremely low. Coolant fan always comes on when needed and when it is overheating the air off the fan is cool not hot like hoses. Heater blows hot as can be. If you smell the coolant after it cools down it smells like exhaust gas but exhaust gasses should cause the coolant to superheat and cause overheat while driving. Its possible head gasket which a new one and have the cylinder head milled could fix. But for some reason I think the cylinder wall could have a hair line crack in it. I know a block test could verify exhaust gasses in coolant but is there any way to check specifically the block with out disassembly of engine. Would like you opinion on the matter cause frankly this is blowing my mind. Appreciate it.