on the 97 SSEi

Cruising down the road, the temp needle begins straight up (200) and climbs to the next hash mark, pauses, the falls to the straight up position. Then the cycle repeats. The cycle is less than a minute, but more than 30 seconds, so you can watch the needle move.

i wouldn't say theres anything wrong with your cooling system. id say something like the temo. sending unit or the sensor itself i had this problem with my other car.. eh dont know if that helps..

I may be going out on a limb here, but....

That'* your thermostat working properly.

Just replace you're thomostat with a 180* one. Its better for a */C'ed engine anyways. Keeps it cooler.

I just don't recall the temp swinging that much on other vehicles

I've heard that once something is replaced on the cooling system it will do that. Don't quote me on that though. BTW- you're the first 200K+ mileage Ser 2 supercharged i've seen. How she running at that mileage? Where in MN do you live?

You say that you are "cruising down the road". Is that the highway or local stop and go traffic. When travelling on the highway it should be a constant needle(about 200) but in stop and go traffic it would be normal for it to go up and down with the cooling fan kicking on and off,

Ol' Timer, on the highway, 60, cruise control

Fan, runs smooth as silk, start easily in the winter. In fact my remote start is set for .5 sec crank and it has never failed to start right off this whole winter.
Mileage during the summer averages 30mpg, but have gotten more on the freeway.
Montevideo, I get to Lakeville quit often, have a sister-in-law there, sister lives south of Burnsville.
As far as changing anything I haven't. The only thing I've done is change oil, dropped the tranny pan once(new filter, oil), plugs and wires. I did run one of those top engine cleaner machines once, and have to say I felt the difference. I'm thinking of doing it again, that was at about 120,000

I don't think you have much to worry about. But you might want to change the thermostat and, while the thermostat is out, flush the cooling system. Then put in a new 195 thermostat(I like it warm in the winter) and put in fresh coolant(your choice of colors). And since it'* YOUR money, you might want to replace the upper and lower radiator hoses at this time too.

I changed my thermostat from a 180 back to 195 because my milage went down about 2 mpg. My gauge was rock solid at 180 unless I was stuck in traffic, and with the prior 195 it was solid at 195. Now with the (second) new 195, my gauge moves like as described in the original post, and it does it while stopped or moving 50 mph. The only thing that was changed was the thermostat. Since this started, I've changed the temp sensor, and radiator cap. My system isn't losing coolant and is holding pressure. I'd appriciate any ideas. Thanks, Mark