You didn't say if it was getting too hot in traffic or running at speed.
I guess your rad looks like this?
https://www.ebay.com/itm/394081506624?c ... 31544fcf6cZero experience with purple ice but special coolants are a temp(orary) solution. Like the pun? I do!
Baffling around the radiator is a major factor for cooling above 45mph. I'll assume you are running the R1 cooling fan and the r1 thermostat has (hopefully) been removed with the installation of the inline thermostat, which should be 180f to provide some cushion if overheating is just a matter of time.
You could add an expansion tank to increase the system volume which helps. Another option is to fit an automotive radiator with reducers to adapt the hoses and a better cooling fan. The civic is very common:
https://www.ebay.com/itm/374244842190?f ... R8Tbi-vlYAR1 Core: 15.35 " x 9.34" x 0.87", 1 row, 144.77 sq in surface area, volume 124.73 cubic inches, 1" inlet and outlet.
Civic core: 14.25" x 13.75" x 1.50", 2 row (can be three row), 195.93 sq in surface area, 293.90 cubic inches. 1.25" inlet and outlet
Scion core: 19.75" x 14" x 2.0", 276.5 sq in surface area, volume 553 cubic inches, 1.25" inlet and outlet.
You might just check the stat temp and add an expansion tank to see how that goes.
Something like this if you have room:
https://www.ebay.com/itm/312606264708?h ... R-KQ-uvlYAA reducer. You just add a short piece of 1 inch od pipe and a couple clamps to reuse your hoses. They come bent too if that helps the fit:
https://www.ebay.com/itm/334300334874?h ... R47CqOzlYA
_________________
Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS
viewtopic.php?f=5&t=13225&p=134742Simple Spring select
viewtopic.php?f=5&t=11815LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12