Ive just had my car serviced. But my mechanic told me that there's some gunk in the coolant tank used to sometimes block leakages(dunno what it's called). Also found condensation on the oil cap! Im getting a mechanic to get the head gasket tested in the weekend, and my uncle who's a mechanic has advised me the car is fine but I'm doubtful. Any one else had this? Im in a flap as to what to do! Any help would be appreciated.