I wrote earlier asking about the fan test regarding my hot-running
diesel. I got lots of great advice and links. However, I just drove if
to a meeting a mile or so away in  light traffic, shut it off, attended
the half hour meeting and drove it back.

the temp needle was swinging pretty high by the time I got back. I also
watched it rise dramatically just a few blocks from home, the dramatic
rise slowing at mid-range but continuing to rise till I shut off the
engine.

Then I drove home, same thing. Never let it get all the way hot, but I
could smell hot coolant when I arrived.

One list member mentioned checking after a short ride for an air
bubble. I did, and pure coolant came out. I noticed, however, that the
bottom or the radiator was lukewarm, and everything above that was cool.

Stuck thermostat? Obviously the water pump was working pretty good to
pump water to the top of the radiator.

What is involved in changing a thermostat?

Thanks,

Jim