Fan Sensor

["Mike Razor" <mrazor@mis.net>]

Put in new grommet, new sensor and got a white plug in from a buddy
with an old MG parts car. The thing still wants to pop out! Could an
overfilled expansion tank cause this? Someone suggested that I take
one of the clips off the heater and use it to brace the sensor in. Not
sure my untrained eye sees how it is done.
Any suggestions?
THANKS MUCH!
Mike R