94 cav overheating

So far I have replaced the radiator, water pump and t stat. Currently I'm running with no stat and it still will run to the middle mark and higher on the highway. It doesn't lose any coolant and the oil is clean. What am I missing?

So far I have replaced the radiator, water pump and t stat. Currently I'm running with no stat and it still will run to the middle mark and higher on the highway. It doesn't lose any coolant and the oil is clean. What am I missing?

are the cooling fans working? will it acually overheat(red line)or is it just
going a little past 1/2 way.was the system clogged & you replaced rad,pump ect. make sure area in front rad condenser clean from leaves ?

Yes, the fan is working and I have made sure the front is clear. It overheated (almost to the red) two weeks ago. I was on the interstate and was in some serious hills. I pulled the t stat and limped home with the temp staying in about the middle. It used to always run on the first mark. My next thought is a plugged heater core. Gonna bypass it today.