Thermostat & coolant drain procedure

[dlmrun2002]

Well of course with winter looks like my thermostat is stuck open. Some heat but could use more. Car warming up to 10 o'clock instead of 12. So I am thinking I only need to drain enough coolant just below the thermostat level on the car to swap thermostat stat. Is this right? Why drain the whole thing if I don't have too?

dlm dog ny

1974 2002 L Jetronic efi
1989 325iX- needs thermostat
1991 318is

[jlevie]

If all you are doing is a thermostat change, a complete drain of the system isn't required.