I am due to have my thermostat changed this weekend and I have recently seen that my coolant is all frothy? I do short journeys (6 mile to work and back) however there is no white mayo type substance on the underside of the oil cap. However I do have a slight oil leak. Car drives normally (apart from slight lack of power which I presume is the thermostat affecting fueling/boosting. I have read a lot about head gasket issues relating to this and any help would be welcomed. Thank you.