I had the same thing happen. That is not a temp sensor, but a fluid level sensor, and the aftermarket ones are TERRIBLE. Try to get one from a dealership if possible. Perhaps a big threaded pvc pipe fitting can be used to plug the hole and get you back on the road, but I have not looked into this. I would be good to know if there is a way to plug the hole in emergencies and keep one in the van.
 
> Date: Thu, 9 Jul 2015 11:22:46 -0600
> From: gkaust@GMAIL.COM
> Subject: Logan Pass - blew the expansion tank temp sensor
> To: vanagon@GERRY.VANAGON.COM
> 
> Rather an exciting day at the top of Logan Pass in Glacier National Park
> yesterday. Wanting to get an early start we arrived at the top of Logans
> Pass from the east and in the parking lot by 7AM on a beautiful clear
> morning. Nothing unusual going up the pass except for slightly high
> temperature.
> 
> Steam and coolant spilling out the back and onto the parking lot.  Tried to
> cleanup as best as possible using towels and paper towels. Within minutes
> the mountain sheep arrived to try to lick the coolant from the trail of
> coolant in the parking lot and about 50-100 yards of coolant on of road.
> Spent the next 1.5 hours chasing the sheep of the road from one end of the
> spill to the other until the Park Ranger arrived. Got many people upset
> wanting to take pictures until we explained what we were trying to do. The
> biggest ram, named Randy by the park ranger, stayed around for the next +4
> hours taking every opportunity possible to get back on the road to lick up
> the coolant. Apparently the animals are there every morning to check the
> parking lot for coolant and the ranger suggested that the animals knew our
> leak before we did just by smelling the air.
> 
> After the ranger arrived I managed to find my problem  - the temperature
> sensor had broken at the threads, and popped out of the expansion tank and
> I knew I wasn't going to be able to fix it especially without access to a
> phone or wifi.  We were forced to have our Westy towed down the west side
> of the pass to Kalispell. We had hoped to get a flatbed truck but that
> didn't happen - nevertheless it was quite the ride going down the west side
> of the pass. Fortunately we have AMA (or AAA in the states).
> 
> We are currently in Kalispell, the Westy (named Westley by my wife; based
> upon the movie line in Princess Bride "my one true love") is at the
> Autohaus in Kalispell. The part is on order and we hope to be on the road
> tonight.
> 
> I'm not much of a mechanic, and surprised the shop didn't have a look at
> the engine. They seemed to be comfortable with my interpretation of what
> happened.  They quoted me roughly $350 for work that needs to be completed
> which seemed excessive but it was explained to me that it will take some
> hours to ensure that all the air bubbles will need to be cleared. I'm
> hoping that there hasn't been any damage to the motor with such a sudden
> loss of coolant even though appeared to shut-down normally. I mentioned
> that the fan is pretty load on high but after receiving a quote of $600
> plus 4-5 days for the part I turned that down.
> 
> We are still hoping to make to the west coast (Washington and Oregon). If
> you have anything I should be aware of, recommended repair shops on the way
> to Oregon, or things we should see let me know.
> 
> Goetz
> 1987 Westfalia (Westley)
> 
> 
> 
> ,