My truck had a good size coolant leak the other day someone told me its the radiator cap on the expansion tank.Bought a new rad cap the leak was gone or so I thought.after I drove my truck for about a half hour came home parked my truck for 4 hours went outside and now the leak is still there its now just smaller its the size of a quarter with the new radiator cap on.what could be causing this leak?

 

If there is too much coolant or you overheat, it is supposed to overflow and it has to go somewhere

 

thats true but there isnt to much coolant its below the fill line.