I have just finished installing a new water pump, expansion tank, some
hoses, etc. in my '90 Westy and was getting ready to bleed the system when I
discovered a coolant leak at the temp sensor (I?), the black one facing
forward. Is the 'O' ring for this one the SAME SIZE AS FOR THE TEMP (II)
SENSOR? That one was replaced earlier this year, but it was NOT leaking and
I have the old 'O' ring. Also, how much coolant am I likely to lose while
swapping  'O' rings?? I don't have much to spare.

Thanks for any and all help.

Jerry