2002 a4 1.8t just tuned up at 74kmiles ,water pump replaced,timing belth ,termostat,idler,serpentine and both coolant temperature sensors,but every 2 to 3 days a get engine light on with the code-p1296 wich is cooling problem.the hose on top of the radiator is firm and hot but the bottom hose is almost cold.When i open the bleader screw on the top the only thing that is coming out is steam and air bubles and very little coolant.Could this be a head gasket problem or something else.Please any help is greatly appreciated.