Your radiator also might simply be old getting a bit clogged and losing its ability to bleed off heat at the environment.
One trick from the street race community I was a part of many years ago was:
-to refill the raditor with a thinner mix ( instead of 50/50 coolant/distilled water maybe closer to 40/60. If you are using premixed coolant then dont top it off with premix but top it off with distilled water.
This increases the heat capacity of the radiator effectively enlarging it a bit
- but the above has to be in conjunction with adding a bottle of this product
https://www.sandtler24.de/red-line-wate ... o4EALw_wcB
What this does it changes the surface tension of the coolant. Resulting unless bubble formation at the cooling fins inside the radiator and hence better heat transfer. Also it is said to reduce cavitation at the water pump.
Lot of street racer folks who run stock radiators but added after market turbos do this little trick to avoid buying/installing bigger radiators.
What are the tradeoff? A thinner mix will have to be replaced more often is more susceptible to boiling over at a given temp. but enough people whose judgement I trust do this. I have also done this many times when running stock radiator in a 350Z and with supercharger take the power from 300 at the crank to nearly approx 480 at the crank.
So I figure this trick may help an old radiator transfer heat more effectively.