Ron,

You will lose some coolant. When I swapped mine I used the advice of Ken
Wilford.

1. Remove the wiring
2. Remove the metal clip
3. Have the new senor with the o-ring on it ready
4. Quickly remove the old and insert the new.

If you time it right you won't lose too much. I bled my system after I did
it but it didn't appear that it needed it.

--
Thanks,

Jeff
'90 Carat (Grover)
'86 (We call this one Parts)
'85 GL (Preparing to move to a new Home)
'78 Bus (Melissa) Patty's Bus