my car runs for about 15min and then blows the water out the header tank cap. It doesnt empty it all just whats in the tank,it is not getting hot and only does it on track,

 

When you say "not getting hot" do you mean the water itself or the engine?
Might simply be a blocked pipe (air) causing a build up of pressure then blowing the cap. Can you feel the water flowing round? Check to feel how hard the water pipes are around the front. Not sure why it wouldn't do it off track tho.