Blown head gasket? Stop leak additive? Can anyone tell anything from these photos? Ive got car parked doing alot of maintenance and i pulled the radiator hoses to put in new thermostat and new hoses and saw this grimy,gritty paste residue in the hoses. Before parking my car months back it was not overheating, ran fine, oil looked normal when i drained it for maintenance. My plan was to go on with timing belt service and oil pump reseal but now in wondering if i should put everything back together and run it a bit and rule out a head gasket failure