I just replaced the thermostat on my 97 1500 because it was stuck open. I replaced it with a 195° fail safe and now its running at 210-220. I also replaced the coolant temp sensor and intake manifold temp sensor. Could it be low coolant or air trapped in the cooling system?

 

I don't like the fail safe stats. They tend to fail far to easily. Your gauge is showing a bit warm, but, with the new sensor..... that may be where it sits now. If you have a scanner that can read live data, plug in, and once the engine is fully warmed, see what the PCM thinks the temp is.

 

That seems like a normal operating temp to me. Could be a little cooler but nothing I would be to worried about. Like HY said. Get a good scanner and see what it says..

 

I'm not too worried about it as long as it doesn't affect how it runs or anything like that. When I first got the truck it had a regular 195 thermostat and it stayed right at 195. I replaced it with a fail safe when I changed the plenum and it ran at 210 but it was a 195, and now its running a bit hotter with the new one at 220-230. The temp changes when I stop and go and I don't know if it has to do with the fan speeding up or what.

 

I'm a huge fan of Stant Superstat thermostats. They are highly reliable and not prone to premature failure or wide/varied temperature swings.

I believe this one fits 5.9 magnum engines -

 

I'm messing with it today and the radiator hose that connects to the thermostat isn't getting hot until 220 degrees and I guess that's when the thermostat is opening up because I had the cap off and watched it suck the coolant down in there. Isnt it supposed to get hot as it warms up? Its also taking forever to get to temp

 

Thermostat should be fully open by the time it reaches its advertised temp, if yours isn't opening until 220... it's bad.

 

Sounds like air trapped in there, T stat doesn't open because of the air at the top where the t stat is. Plenty of posts on this. Drill a hole in t stat body it will let the air out. Look at post 14 here.