Engine overheating

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I have an s14 with a 1jz in it and recently it just started overheating and not really sure why?

The car warms up just fine, and you can let it sit and idle and it won't go over 90 degrees Celsius. If i go on a drive and let it sit at a long red light or let it idle, it will start to over heat and head towards the 100's..

I did a track day yesterday, and halfway through the track my car was hitting 110 degrees Celsius. I couldn't go one lap without the car overheating..

I have a koyo radiator, and 2 10" radiator fans wired to my ignition. The only thing that i think it could be is maybe that i am running no coolant over flow tank? i'm just running a hose to the side of my car, so maybe air is entering my coolant system?

it recently started doing this, i used to rail the hell out of the car and it was fine, no overheating.

I already tried removing the thermostat and running it on the track, and it didn't help much at all.

Any help would be great.