well my mech fitted the new thermostat and I got a new header tank!.
but I went for a drive a few days later after I checked the coolant level,
and it was still pushing the new coolant out of the expansion tank the one
near the battery!.
the coolant goes down in the header tank to the expansion tank but does Not
go back to the engine or header tank! what is going on??.. .

should I put a old thermostat in with the stat part open so coolant flows
around the engine ect.. . and block the expansion tank over flow pipe on the
top off??.. .

is it a good idea to to do this??? .. .

help please......... .