Hi
I have decided to replace the coolant sensor  I have the sensor
 but
have not installed it yet.  It doesn't have threads and appears to be
held
in place by a clip.  Is it possible to switch from old to new sensor
fast
enough to avoid spilling a lot of coolant, or is it necessary to drain
the
coolant from the block first?  Is any form of sealant or O ring
replacement
needed??  My Bentley manual doesn't seem to say anything about this
apparently minor repair.

Any sharing of experience would be appreciated. Merci
Alain Thibault
Westfalia 1991