Yo!
have him check how tight is the sensor (loose or not!!!!), if still tight,
he can drive around.... easy fix is a new O-ring and/or Epoxy glue.

To answer your questions:

1)-Air doesn't get into the sytem, it goes outside and you are loosing
pressure, but that's not so bad when it's in the expension tank. loosing
pressure can become a problem if to high. Keep the throttle low.

2)-Good shop anywhere in BC, more on Vancouver island, not a problem at all.
Many westy overthere.

4)- Yes, they crack easily.... but it's easy to see the crack normaly.

Cheers, Ben
http://www.benplace.com/

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1) Any problems driving around like this for a few days? I told him to just
keep adding water to the expansion tank and it should be ok...but I wondered
if air could get into the radiator and cause some hot times.

2) He has to drive through Vancouver and Seattle (or at least around it) to
get back to SLC. Any list vendors or list nice guys have these parts in
stock so he could just pick them up and be on his way (oring and sensor)?

3) If no one up there has the parts (at least on the list) does anyone have
a good recommended shop I could call and order the parts so he can pic them
up in few days?

4) Could it be something besides the o-ring? Possibly a crack in the tank
(I've had one of those....).

Thanks,