Thermostat is 195* so the operating temp should be around there, close to straight-up "noon" on the gauge or maybe a needle's width below 200 mark when fully warmed up. It will go up a little bit above 200 (e.g., 200-220) if pushing things like towing or going up mountains in the summer time.
I'm having same problem as you and have been for ~25k miles ever since the timing belt job at 100k miles, which included coolant replacement along with the water pump replacement. Before that my van warmed up fairly quickly and needle more or less stayed straight up near 200*. Now it takes much longer to warm up and the needle bounces around somewhere between 170 and 195 pretty much constantly while driving. Even did it during middle of hot Georgia summer when ambient temps were in the 90s. When idling in garage or driveway for long periods it will stay at 195 though, or even creep up slightly over 200, but not by much before dropping back down to 195. But when driving around the needle bounces around 170-195.
I went around in circles on this with the mechanic who did the timing belt, and he says it's perfectly normal, but then he can't really say why it didn't do that before the timing belt/water pump job at 100k miles.
Top offenders would be bad radiator cap or thermostat is stuck open or bad coolant temp sensor. So at around 110k miles I had all three replaced (by another mechanic), and I was certain it would 'fix' it and things would go back to normal. But it kept doing the same thing with long warm-ups and the needle bouncing around 170-195*.
Then I had a radiator leak last summer at 116k miles and I had the radiator replaced. I suspect air was trapped in the system the whole time causing the temp to misread, and hence the needle bouncing around. Air pockets will also cause extreme heat increases which could also explain the radiator springing a leak. So I was optimistic that the temp problem would go away after the radiator was replaced. But no - same thing with needle bouncing around between 170-195*.
At 119k miles I had another coolant leak at the Y-tube diverter. Very common problem (see other threads). Had it replaced with metal Y-tube and new hoses/clamps. Again, I thought this could have been the source of air in the system. But it's still doing the same damn thing with long warm-ups and needle bouncing around between 170-195*.
I am at a loss at this point, but I suspect there is still air in the system. Or I got a bad t-stat or coolant temp sensor or rad cap when I had those replaced. This is not normal behavior though. Although based on number of posts about it on the Chrysler minivan forums, it is not uncommon behavior. But not normal.
