Even with a new tank and a new sensor, with both being plastic of sorts,
there can be "Thread" resistance making it difficult to tell when the
sensor is "Good and snug" against its seat.  This can be worse when
putting a new sensor into an old tank.

Inspect your old tank carefully and make certain it isn't cracked.

I always put Vaseline on the threads and the O=Ring.  It allows it to
screw in really easily and you can tell when the O-Ring makes contact
with the tank.  Like with other rubber O-Ring on plug applications, it
doesn't take a lot of torque.  You just want to make a water tight seal
and no more.

Mike

Thomas Pfrommer wrote:
> Hi,
> I discovered today a small leak on my coolant level sensor. I assumed a
> bad O-ring and stupidly I wanted to tight it down a bit further until
> tomorrow to get  new sensor. Well surely another 1/16 of a turn and the
> plastic broke and I had to get home via public transport. Now I will get
> this part tomorrow (hopefully they have it in stock at VM Authaus in
> Vancouver / Burnaby ... a really great place to get reasonably prized
> parts the next day by the way .... and a really nice guy .... no I am
> not at all involved with this mechanics, its just a good place to get
> things fast).
> Now I thing when I changed the expansions tank a few months ago it is
> very likely, I might have tight the sensor a bit too much so that it
> slowly cracked and not the O-ring but an already broken plastic was the
> leaking problem in first place. My wrench did the rest then hehe. I
> know, next time I should inspect first before tighten it more.
> Is there a rule of thumb how to tight down these plastic sensors? How
> many (fraction of) turns after it is hand tight? As I have to use a 32mm
> socket it is quite easy to over torque it without even knowing ...
> Thanks
> Thomas
>