Occasionally my rad is steaming from the upper left hand corner. Can smell coolant. Small amount that comes and goes. Can't pinpoint the leak. No drop in fluid that I can see. I know I should get a rad pressure test, but not ready for that yet. What could be the cause? Airlock?

 

Radiator pressure test at 10 psi with soapy water is the best way to tell if you have leaks in hoses or the radiator itself.