My 93 accord's temp gauge has recently started nearing the 3/4 mark or slightly higher when highway driving. The thermostat was replaced but did not solve the problem. I had a little leak in my radiator so I put some of that liquid radiator leak stuff in it. The problem started not too long after that.
Could it be a partially clogged radiator? I've read that an air pocket in the engine could be the culprit as well.
The temp gauge rises when the car needs the most coolant it seems. I can drive around town at 30-50 MPH and the gauge remains at the 1/4 level.
It's when I'm highway driving that the issue arises.
I've checked the coolant level and it looks ok.
Before I start looking at the head gasket and water pump I'd like to eliminate some of the smaller potential causes.

Thoughts??

 

I would put in a 170 degree thermostat. You probably have a 180 or 190 installed. you may have to switch back in the wintertime if you live in a cold location. The air bleed is on the thermostat housing.