when i got my starlet it had a burst radiator. and the coolant bottle was constantly empty. i ran it like this for 2 months and it had run with it for a long time before i got it cause the rust was ridiculous under the bonnet. never had any problems. the temp guage remained at half. my radiator coolant seemed to drop to a certain level and then remain there. so it is possible to run it without, as long as you top it up frequently. Edit. Not to second guess rick by the way as i'm not sure how safe it is on a track car, which i assume will get hotter