Hey guys I have a weird issue with my 02 3.4 monte, I drove to Texas a few weeks ago and the temp gauge started to creep up depending on how fast I drove, at 60 I had no problems the needle pointed to about the halfway point but 70 and 80mph would cause the temp to slowly rise to round the 3/4 mark or more but as soon as I started slowing down the temp would start to come back down too. I did some maintenance before and after my trip and so far nothing as seemed to help, I replaced all the coolant along with a new overfill tank, new 180 thermostat, straightened the fins on the condenser, filled cooling system with water and purple power thinking the radiator might be clogged, flushed cooling system again and filled with new antifreeze. Now I've had the for around 4 to 6 months and it has 180000mi on it and it looks like someone had replaced gaskets on it as some point in time because I can see red RTV where the intake meets the heads. I did find a small amount of black oily residue inside the radiator which is why I decided to flush the cooling system with a degreaser but other than that the car runs great I drive it everyday I just wish I could drive faster than 60. I have owned a 96 monte and had to do head gaskets on it so I'm hoping this issue isn't pointing to bad head gaskets

 

That RTV you saw may not have been from a head gasket job. Very possible someone had to replace the lower intake gaskets.
As for the temp issue, after this experience, did you check the radiator to see if you needed to top it off? It is not uncommon for these to have air pockets that cause weird gauge issues. When filling, there is at least one, if not two bleed screws for the 3400 that it is helpful to open to help reduce the change of air pockets. I know one is on top of the black goose neck coming from the water pump housing, I believe there is another one on the thermostat housing as well. If you open the bleed valves, just keep filling the radiator until coolant is dribbling from the bleed valves.

Also, double check the gauge reading with a scan tool. The stepper motors that drive the gauges are known to have problems over time.

 

I'll check for air pockets again but both times the radiator was filled I made sure to open both bleeder screws, I have a bluetooth OBDII scanner that I use with the torque app so I'll double check the temp gauge accuracy also, but I think you are right that only the LIM gaskets were replaced and not the head gaskets, any other ideas you guys have I would for sure like to hear them.

 

Any other gauges/dials going wonky, like speedometer, oil pressure, even occassionally? if so, it could well be the stepper motors in the dash.