I replaced my OEM radiator with a high quality aluminum radiator and my temps were always extremely low until I took it to a paint shop to have it repainted and it spent 5 weeks there and got it back today and my temps on my gauge are high now. Does anyone know why?
Are we talking paint the car or paint the radiator?
Radiator paints are made to go on thin (old school recommends lacquer not enamel) and you only shoot one angle from top so it looks black but doesn't coat in between fins.
If the paint shop used automotive paint on radiator and did it throughly from both side and all directions (like painting a fender) it can effect how well it dissipates heat. Even if they just over spayed it a bit and touched it up with spray cans
When you reinstalled the radiator did you get all the air out of the system? Sometimes it can be hard to get it all out. If you have air pockets in the system it can cause over heating issues.