These sensors can take a set over the years or the o-ring for them can
take a set.  I have found that if I am replacing the tank I always
replace the sensor as well since I have tried using old sensors in new
tanks only to have them leak.  The other source of the leak can be the
tank itself.  Sometimes there are hair line radial cracks around the
hole where the sensor screws in.  I install the new sensors to snug
tightness and that is it.  Tighten beyond snug at your own risk.  If you
have a good sensor and a good tank you will be good to go.  If the tank
has turned yellow to the point that it is opaque (you can no longer see
the coolant level easily in the tank), the tank is dying and should be
replaced.  Every single one that has been coming in here lately that is
yellow has a radial crack at the base of where the pressure cap screws
on.  Many times the crack isn't a through crack yet, but a good rule of
thumb is that if you see a crack, then it needs to be replaced right
away.  I know they can last for years afterward, or they can go
tomorrow.  Why take the risk?

Have a great weekend!

Ken Wilford
John 3:16
www.vanagain.com

On 4/28/2012 3:19 PM, Edward Maglott wrote:
> I have a small leak at my '86 Vanagon.  Just a seep really.  I
> removed it and don't find any obvious defect in the sensor, the tank
> or the o-ring.  I've cleaned all the parts and am just going to try
> putting it back together and see if it still leaks.  Can't find any
> torque value in the Bentley.  My best guess is just to make it
> "fairly snug" but is there an actual value listed anywhere?
>
> Thanks,
> Edward
>