First off, I'd check the water level is ok. Then I'd check the thermostat if theres one there, sounds like it isn't allowing the engine to warm up. The temp should go up if its on idle for a while though, it'll warm up quicker with the car heaters off. I am running my motor without a thermostat in coz the idiot in the shop sold me the wrong one, the old one was in bad shape and wasnt doing it's job very well at all. The temp stays under the white mark until I hit traffic. Whilst waiting for it to warm up it's a good time to see if the cooling fan cuts in too as it should. Better than finding out in traffic that it's not.