Coolent temp Goes to regular temp and drops down?

I just did the lower and upper intake gaskets on a 2000 grand prix and flushed the antifreeze out and now it does not run hot, it goes up to the first bigger line on the temp guage which on my other grand prix is normal temp but on this other one it drops back down. The car never gets hot just goes up to the first line and goes back down any ideas there? Thanks

I'm reading you saying ...it goes up then goes down. How far, what temps are those marks. Not being a jerk...trying to get enough info to understand how low etc it's dropping.

Sounds like you need to bleed the cooling system. There's air in it from what you describe, barring any wierd temps that Bill is asking for.

If there was air in the system then it would be running hot

Air in the system would make the car get REALLY hot, then very suddenly get pretty cool. Like a temperature swing from 235-190 all at once. My L36 Camaro did that to me a few times.

Since he's saying the first line on the temp gauge I don't think that he's overheating

Is your motor the 3100?
Sounds like major air in your system or your thermostat is broke open.
I'd replace the thermostat and gasket since they are cheap, then bleed the car the old school way jacked up with the rad cap off.

The temp goes up to the first bigger line then drops back down to the middle of 160 and that bigger line. Does that back and forth. I already replaced the stat with a good one. I have just never seen this before. Maybe a bad stat?

BTW guys..our coolant sensors suck at reading air temps of the LIM. So if you don't have enough coolant to cover the sensor..it can read cool while overheating from lack of coolant.

It sounds like you have some air in the sytem, you should bleed it