ongoing problem with a d2 td5,no gurgling from heater matrix now(got rid of the air)changed the thermostat,when I have a few revs nice and warm,on tickover heat is only just warm temp gauge is in the middle,any ideas please.

it still seems like air in the matrix...airlocks in the matrix can be very 'stubborn' so maybe you just think you've got rid of all the air... when the engine is cold undo partially the bleed screw and keep the engine rev'd above 1500 untill no bubbles are coming out there... if no joy go for a short ride with the tank's cap removed but just untill the gauge goes up to the middle... take some coolant with you to top up if some will be lost.

sorted it,head gasket has gone,was'nt showing any symptons had it tested just to rule it out,get it back Tuesday,being lazy and having it done only £300.