Hi everyone!

I'm having an over heating issue but only between 55-65mph. Anything higher or lower the car is perfect. I've sat in traffic with absolutely no issues but the moment I hit 55-65mph the temp gauge will slowly raise until I either slow down or go faster.

Older dual core koyo rad (new cap)
Coolant reroute
Removed all a/c components
No heater
180 thermostat
No belly pan (been lazy to modify it)

Bad thermostat? Water pump? Coolant levels are constant and I've bleed the system many times with that special funnel. I'm about to take out the thermostat and see what happens.

 

Put the belly pan back on

 

​​​​​​This. Without the under tray, you can't draw enough air across your radiator. I'm always surprised how many people ignore the importance of the under-engine aero in cooling. You need the under tray to create a low pressure zone so air is drawn through the radiator. Without the under tray, you have high pressure at the front of the radiator, and high pressure in the engine bay. No pressure Delta means no airflow.

 

Ok, belly pan is going on tomorrow

 

yeah but you get lower in bay temps at idle!