i was checking under the bonnet and noticed that my coolent was a rusty colour, i drained the coolent from the radiator and topped it back up with new coolent, Ran it for a couple of days and checked it again and it was still rusty coloured so i took the thermostat out and check it realising that the thermostat was permanantly shut,i don't know how long this has been like this would it have caused any problems.
as long as there is no milky residue under the oil filler cap or on the dipstick (this would indicate that the head gasket has blown )and the car has not exesivly overheated all should be ok . but would suggest flushing through several times with clean water before topping up with mix
Did you test the thermostat in a cup with boiling water ? I take it you know the thermostat would be in the closed position which is normal when you removed it and it only opens fully when it reaches temp on thermostat .If thermostat was permantly closed , you wouldn't be long in knowing about it .